units: scrub encoder/decoder layout

diff --git a/units/src/amount/unsigned.rs b/units/src/amount/unsigned.rs
index 7b150fa3..2ebf85a5 100644
--- a/units/src/amount/unsigned.rs
+++ b/units/src/amount/unsigned.rs
@@ -613,16 +613,10 @@ impl TryFrom<SignedAmount> for Amount {
     fn try_from(value: SignedAmount) -> Result<Self, Self::Error> { value.to_unsigned() }
 }
 
-#[cfg(feature = "encoding")]
-encoding::encoder_newtype_exact! {
-    /// The encoder for the [`Amount`] type.
-    #[derive(Debug, Clone)]
-    pub struct AmountEncoder<'e>(encoding::ArrayEncoder<8>);
-}
-
 #[cfg(feature = "encoding")]
 impl encoding::Encodable for Amount {
     type Encoder<'e> = AmountEncoder<'e>;
+
     #[inline]
     fn encoder(&self) -> Self::Encoder<'_> {
         AmountEncoder::new(encoding::ArrayEncoder::without_length_prefix(
@@ -631,6 +625,21 @@ impl encoding::Encodable for Amount {
     }
 }
 
+#[cfg(feature = "encoding")]
+impl encoding::Decodable for Amount {
+    type Decoder = AmountDecoder;
+
+    #[inline]
+    fn decoder() -> Self::Decoder { AmountDecoder(encoding::ArrayDecoder::<8>::new()) }
+}
+
+#[cfg(feature = "encoding")]
+encoding::encoder_newtype_exact! {
+    /// The encoder for the [`Amount`] type.
+    #[derive(Debug, Clone)]
+    pub struct AmountEncoder<'e>(encoding::ArrayEncoder<8>);
+}
+
 #[cfg(feature = "encoding")]
 crate::decoder_newtype! {
     /// The decoder for the [`Amount`] type.
@@ -651,13 +660,6 @@ crate::decoder_newtype! {
     }
 }
 
-#[cfg(feature = "encoding")]
-impl encoding::Decodable for Amount {
-    type Decoder = AmountDecoder;
-    #[inline]
-    fn decoder() -> Self::Decoder { AmountDecoder(encoding::ArrayDecoder::<8>::new()) }
-}
-
 #[cfg(feature = "arbitrary")]
 impl<'a> Arbitrary<'a> for Amount {
     fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
diff --git a/units/src/block.rs b/units/src/block.rs
index 8978df6a..08657b40 100644
--- a/units/src/block.rs
+++ b/units/src/block.rs
@@ -204,13 +204,6 @@ impl TryFrom<BlockHeight> for absolute::Height {
     fn try_from(h: BlockHeight) -> Result<Self, Self::Error> { Self::from_u32(h.to_u32()) }
 }
 
-#[cfg(feature = "encoding")]
-encoding::encoder_newtype_exact! {
-    /// The encoder for the [`BlockHeight`] type.
-    #[derive(Debug, Clone)]
-    pub struct BlockHeightEncoder<'e>(encoding::ArrayEncoder<4>);
-}
-
 #[cfg(feature = "encoding")]
 impl encoding::Encodable for BlockHeight {
     type Encoder<'e> = BlockHeightEncoder<'e>;
@@ -222,6 +215,21 @@ impl encoding::Encodable for BlockHeight {
     }
 }
 
+#[cfg(feature = "encoding")]
+impl encoding::Decodable for BlockHeight {
+    type Decoder = BlockHeightDecoder;
+
+    #[inline]
+    fn decoder() -> Self::Decoder { BlockHeightDecoder(encoding::ArrayDecoder::<4>::new()) }
+}
+
+#[cfg(feature = "encoding")]
+encoding::encoder_newtype_exact! {
+    /// The encoder for the [`BlockHeight`] type.
+    #[derive(Debug, Clone)]
+    pub struct BlockHeightEncoder<'e>(encoding::ArrayEncoder<4>);
+}
+
 #[cfg(feature = "encoding")]
 crate::decoder_newtype! {
     /// The decoder for the [`BlockHeight`] type.
@@ -238,13 +246,6 @@ crate::decoder_newtype! {
     }
 }
 
-#[cfg(feature = "encoding")]
-impl encoding::Decodable for BlockHeight {
-    type Decoder = BlockHeightDecoder;
-    #[inline]
-    fn decoder() -> Self::Decoder { BlockHeightDecoder(encoding::ArrayDecoder::<4>::new()) }
-}
-
 impl_u32_wrapper! {
     /// An unsigned block interval.
     ///
diff --git a/units/src/locktime/absolute/mod.rs b/units/src/locktime/absolute/mod.rs
index 99672a24..d2ace8bd 100644
--- a/units/src/locktime/absolute/mod.rs
+++ b/units/src/locktime/absolute/mod.rs
@@ -397,13 +397,6 @@ impl LockTime {
 
 parse_int::impl_parse_str_from_int_infallible!(LockTime, u32, from_consensus);
 
-#[cfg(feature = "encoding")]
-encoding::encoder_newtype_exact! {
-    /// The encoder for the [`LockTime`] type.
-    #[derive(Debug, Clone)]
-    pub struct LockTimeEncoder<'e>(encoding::ArrayEncoder<4>);
-}
-
 #[cfg(feature = "encoding")]
 impl encoding::Encodable for LockTime {
     type Encoder<'e> = LockTimeEncoder<'e>;
@@ -415,6 +408,21 @@ impl encoding::Encodable for LockTime {
     }
 }
 
+#[cfg(feature = "encoding")]
+impl encoding::Decodable for LockTime {
+    type Decoder = LockTimeDecoder;
+
+    #[inline]
+    fn decoder() -> Self::Decoder { LockTimeDecoder(encoding::ArrayDecoder::<4>::new()) }
+}
+
+#[cfg(feature = "encoding")]
+encoding::encoder_newtype_exact! {
+    /// The encoder for the [`LockTime`] type.
+    #[derive(Debug, Clone)]
+    pub struct LockTimeEncoder<'e>(encoding::ArrayEncoder<4>);
+}
+
 #[cfg(feature = "encoding")]
 crate::decoder_newtype! {
     /// The decoder for the [`LockTime`] type.
@@ -431,13 +439,6 @@ crate::decoder_newtype! {
     }
 }
 
-#[cfg(feature = "encoding")]
-impl encoding::Decodable for LockTime {
-    type Decoder = LockTimeDecoder;
-    #[inline]
-    fn decoder() -> Self::Decoder { LockTimeDecoder(encoding::ArrayDecoder::<4>::new()) }
-}
-
 impl From<Height> for LockTime {
     #[inline]
     fn from(h: Height) -> Self { Self::Blocks(h) }
diff --git a/units/src/pow.rs b/units/src/pow.rs
index f5d0e1e5..4fb956f2 100644
--- a/units/src/pow.rs
+++ b/units/src/pow.rs
@@ -302,13 +302,6 @@ impl From<CompactTarget> for Target {
     fn from(c: CompactTarget) -> Self { Self::from_compact(c) }
 }
 
-#[cfg(feature = "encoding")]
-encoding::encoder_newtype_exact! {
-    /// The encoder for the [`CompactTarget`] type.
-    #[derive(Debug, Clone)]
-    pub struct CompactTargetEncoder<'e>(encoding::ArrayEncoder<4>);
-}
-
 #[cfg(feature = "encoding")]
 impl encoding::Encodable for CompactTarget {
     type Encoder<'e> = CompactTargetEncoder<'e>;
@@ -320,6 +313,21 @@ impl encoding::Encodable for CompactTarget {
     }
 }
 
+#[cfg(feature = "encoding")]
+impl encoding::Decodable for CompactTarget {
+    type Decoder = CompactTargetDecoder;
+
+    #[inline]
+    fn decoder() -> Self::Decoder { CompactTargetDecoder(encoding::ArrayDecoder::<4>::new()) }
+}
+
+#[cfg(feature = "encoding")]
+encoding::encoder_newtype_exact! {
+    /// The encoder for the [`CompactTarget`] type.
+    #[derive(Debug, Clone)]
+    pub struct CompactTargetEncoder<'e>(encoding::ArrayEncoder<4>);
+}
+
 #[cfg(feature = "encoding")]
 crate::decoder_newtype! {
     /// The decoder for the [`CompactTarget`] type.
@@ -336,13 +344,6 @@ crate::decoder_newtype! {
     }
 }
 
-#[cfg(feature = "encoding")]
-impl encoding::Decodable for CompactTarget {
-    type Decoder = CompactTargetDecoder;
-    #[inline]
-    fn decoder() -> Self::Decoder { CompactTargetDecoder(encoding::ArrayDecoder::<4>::new()) }
-}
-
 /// Error types for proof-of-work related integer types.
 pub mod error {
     use core::convert::Infallible;
diff --git a/units/src/sequence.rs b/units/src/sequence.rs
index 130a695d..83cf8597 100644
--- a/units/src/sequence.rs
+++ b/units/src/sequence.rs
@@ -258,13 +258,6 @@ impl fmt::Debug for Sequence {
 
 parse_int::impl_parse_str_from_int_infallible!(Sequence, u32, from_consensus);
 
-#[cfg(feature = "encoding")]
-encoding::encoder_newtype_exact! {
-    /// The encoder for the [`Sequence`] type.
-    #[derive(Debug, Clone)]
-    pub struct SequenceEncoder<'e>(encoding::ArrayEncoder<4>);
-}
-
 #[cfg(feature = "encoding")]
 impl encoding::Encodable for Sequence {
     type Encoder<'e> = SequenceEncoder<'e>;
@@ -276,6 +269,21 @@ impl encoding::Encodable for Sequence {
     }
 }
 
+#[cfg(feature = "encoding")]
+impl encoding::Decodable for Sequence {
+    type Decoder = SequenceDecoder;
+
+    #[inline]
+    fn decoder() -> Self::Decoder { SequenceDecoder(encoding::ArrayDecoder::<4>::new()) }
+}
+
+#[cfg(feature = "encoding")]
+encoding::encoder_newtype_exact! {
+    /// The encoder for the [`Sequence`] type.
+    #[derive(Debug, Clone)]
+    pub struct SequenceEncoder<'e>(encoding::ArrayEncoder<4>);
+}
+
 #[cfg(feature = "encoding")]
 crate::decoder_newtype! {
     /// The decoder for the [`Sequence`] type.
@@ -292,13 +300,6 @@ crate::decoder_newtype! {
     }
 }
 
-#[cfg(feature = "encoding")]
-impl encoding::Decodable for Sequence {
-    type Decoder = SequenceDecoder;
-    #[inline]
-    fn decoder() -> Self::Decoder { SequenceDecoder(encoding::ArrayDecoder::<4>::new()) }
-}
-
 /// Error types for input sequence numbers.
 pub mod error {
     #[cfg(feature = "encoding")]
diff --git a/units/src/time.rs b/units/src/time.rs
index 0305d936..94329a6d 100644
--- a/units/src/time.rs
+++ b/units/src/time.rs
@@ -117,13 +117,6 @@ impl<'de> Deserialize<'de> for BlockTime {
     }
 }
 
-#[cfg(feature = "encoding")]
-encoding::encoder_newtype_exact! {
-    /// The encoder for the [`BlockTime`] type.
-    #[derive(Debug, Clone)]
-    pub struct BlockTimeEncoder<'e>(encoding::ArrayEncoder<4>);
-}
-
 #[cfg(feature = "encoding")]
 impl encoding::Encodable for BlockTime {
     type Encoder<'e> = BlockTimeEncoder<'e>;
@@ -135,6 +128,21 @@ impl encoding::Encodable for BlockTime {
     }
 }
 
+#[cfg(feature = "encoding")]
+impl encoding::Decodable for BlockTime {
+    type Decoder = BlockTimeDecoder;
+
+    #[inline]
+    fn decoder() -> Self::Decoder { BlockTimeDecoder(encoding::ArrayDecoder::<4>::new()) }
+}
+
+#[cfg(feature = "encoding")]
+encoding::encoder_newtype_exact! {
+    /// The encoder for the [`BlockTime`] type.
+    #[derive(Debug, Clone)]
+    pub struct BlockTimeEncoder<'e>(encoding::ArrayEncoder<4>);
+}
+
 #[cfg(feature = "encoding")]
 crate::decoder_newtype! {
     /// The decoder for the [`BlockTime`] type.
@@ -151,13 +159,6 @@ crate::decoder_newtype! {
     }
 }
 
-#[cfg(feature = "encoding")]
-impl encoding::Decodable for BlockTime {
-    type Decoder = BlockTimeDecoder;
-    #[inline]
-    fn decoder() -> Self::Decoder { BlockTimeDecoder(encoding::ArrayDecoder::<4>::new()) }
-}
-
 /// Error types for block times.
 pub mod error {
     #[cfg(feature = "encoding")]