util/test: Add string_view constructor to LineReader and remove StringToBuffer

diff --git a/src/test/util_string_tests.cpp b/src/test/util_string_tests.cpp
index dea45f6f..3835904d 100644
--- a/src/test/util_string_tests.cpp
+++ b/src/test/util_string_tests.cpp
@@ -42,12 +42,6 @@ void FailFmtWithError(const char* wrong_fmt, std::string_view error)
     BOOST_CHECK_EXCEPTION(CheckNumFormatSpecifiers<WrongNumArgs>(wrong_fmt), const char*, HasReason{error});
 }
 
-std::vector<std::byte> StringToBuffer(const std::string& str)
-{
-    auto span = std::as_bytes(std::span(str));
-    return {span.begin(), span.end()};
-}
-
 BOOST_AUTO_TEST_CASE(ConstevalFormatString_NumSpec)
 {
     PassFmt<0>("");
@@ -181,7 +175,7 @@ BOOST_AUTO_TEST_CASE(line_reader_test)
 {
     {
         // Check three lines terminated by \n and \r\n, trimming whitespace
-        const std::vector<std::byte> input{StringToBuffer("once upon a time\n there was a dog \r\nwho liked food\n")};
+        std::string_view input = "once upon a time\n there was a dog \r\nwho liked food\n";
         LineReader reader(input, /*max_line_length=*/128);
         BOOST_CHECK_EQUAL(reader.Consumed(), 0);
         BOOST_CHECK_EQUAL(reader.Remaining(), 51);
@@ -206,7 +200,7 @@ BOOST_AUTO_TEST_CASE(line_reader_test)
     {
         // Do not exceed max_line_length + 1 while searching for \n
         // Test with 22-character line + \n + 23-character line + \n
-        const std::vector<std::byte> input{StringToBuffer("once upon a time there\nwas a dog who liked tea\n")};
+        std::string_view input = "once upon a time there\nwas a dog who liked tea\n";
 
         LineReader reader1(input, /*max_line_length=*/22);
         // First line is exactly the length of max_line_length
@@ -224,26 +218,26 @@ BOOST_AUTO_TEST_CASE(line_reader_test)
     }
     {
         // Empty lines are empty
-        const std::vector<std::byte> input{StringToBuffer("\n")};
+        std::string_view input = "\n";
         LineReader reader(input, /*max_line_length=*/1024);
         BOOST_CHECK_EQUAL(reader.ReadLine(), "");
         BOOST_CHECK(!reader.ReadLine());
     }
     {
         // Empty buffers are null
-        const std::vector<std::byte> input{StringToBuffer("")};
+        std::string_view input;
         LineReader reader(input, /*max_line_length=*/1024);
         BOOST_CHECK(!reader.ReadLine());
     }
     {
         // Even one character is too long, if it's not \n
-        const std::vector<std::byte> input{StringToBuffer("ab\n")};
+        std::string_view input = "ab\n";
         LineReader reader(input, /*max_line_length=*/1);
         // First line is +1 character too long
         BOOST_CHECK_EXCEPTION(reader.ReadLine(), std::runtime_error, HasReason{"max_line_length exceeded by LineReader"});
     }
     {
-        const std::vector<std::byte> input{StringToBuffer("a\nb\n")};
+        std::string_view input = "a\nb\n";
         LineReader reader(input, /*max_line_length=*/1);
         BOOST_CHECK_EQUAL(reader.ReadLine(), "a");
         BOOST_CHECK_EQUAL(reader.ReadLine(), "b");
@@ -251,7 +245,7 @@ BOOST_AUTO_TEST_CASE(line_reader_test)
     }
     {
         // If ReadLine fails, the iterator is reset and we can ReadLength instead
-        const std::vector<std::byte> input{StringToBuffer("a\nbaboon\n")};
+        std::string_view input = "a\nbaboon\n";
         LineReader reader(input, /*max_line_length=*/1);
         BOOST_CHECK_EQUAL(reader.ReadLine(), "a");
         // "baboon" is too long
@@ -267,7 +261,7 @@ BOOST_AUTO_TEST_CASE(line_reader_test)
     }
     {
         // The end of the buffer (EOB) does not count as end of line \n
-        const std::vector<std::byte> input{StringToBuffer("once upon a time there")};
+        std::string_view input = "once upon a time there";
 
         LineReader reader(input, /*max_line_length=*/22);
         // First line is exactly the length of max_line_length, but that doesn't matter because \n is missing
@@ -279,7 +273,7 @@ BOOST_AUTO_TEST_CASE(line_reader_test)
     }
     {
         // Read specific number of bytes regardless of max_line_length or \n unless buffer is too short
-        const std::vector<std::byte> input{StringToBuffer("once upon a time\n there was a dog \r\nwho liked food")};
+        std::string_view input = "once upon a time\n there was a dog \r\nwho liked food";
         LineReader reader(input, /*max_line_length=*/1);
         BOOST_CHECK_EQUAL(reader.ReadLength(0), "");
         BOOST_CHECK_EQUAL(reader.ReadLength(3), "onc");
diff --git a/src/util/string.h b/src/util/string.h
index 64b49bb0..da4ce5a3 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -270,6 +270,7 @@ struct LineReader {
     std::span<const std::byte>::iterator it;
 
     explicit LineReader(std::span<const std::byte> buffer, size_t max_line_length);
+    explicit LineReader(std::string_view str, size_t max_line_length) : LineReader{std::as_bytes(std::span{str}), max_line_length} {}
 
     /**
      * Returns a string from current iterator position up to (but not including) next \n