LND

graph/db: convert NodeUpdatesInHorizon to use iterators

In this commit, we refactor the NodeUpdatesInHorizon method to return
an iterator instead of a slice. This change significantly reduces
memory usage when dealing with large result sets by allowing callers to
process items incrementally rather than loading everything into memory
at once.

The new implementation uses Go 1.23's iter.Seq type to provide a
standard iterator interface. The method now supports configurable batch
sizes through functional options, allowing fine-tuned control over
memory usage and performance characteristics.

Rather than reading all the entries from disk into memory (before this
commit, we did consult the cache for most entries, skipping the disk
hits), we now expose a chunked iterator instead.

We also make the process of filtering out public nodes first class. This
saves many newly created db transactions later.

graph/db: add options infrastructure for iterator configuration

In this commit, we introduce a new options pattern for configuring
iterator behavior in the graph database. This includes configuration
for batch sizes when iterating over channel and node updates, as well
as an option to filter for public nodes only.

The new functional options pattern allows callers to customize iterator
behavior without breaking existing APIs. Default batch sizes are set to
1000 entries for both channel and node updates, which provides a good
balance between memory usage and performance.

fn: add Collect+CollertErr function for iterators

In this commit, we introduce a new utility function `Collect` to the fn
package. This function drains all elements from an iterator and returns
them as a slice. This is particularly useful when transitioning from
iterator-based APIs to code that expects slices, allowing for gradual
migration to the new iterator patterns.

The fn module's go.mod is also updated to require Go 1.23, which is
necessary for the built-in iter.Seq type support.

The replace directive will be removed once the fn package changes are
merged and a new version is tagged.

scripts: add gpg key for ViktorT-11

docs: add release note

lnrpc: add XFindBaseLocalChanAlias rpc

Add the new RPC method that looks up the base scid for a given alias.
Given the previous stepping stones this commit is fairly simple, we just
call into the alias manager and return the lookup result.

multi: add base lookup option to AddLocalAlias

We add an extra option to the AddLocalAlias method which only controls
whether we store a reverse lookup from the alias back to the base scid
it corresponds to. The previous flag "gossip" is still maintained, and
in a way supercedes the new flag (it will also store the base scid
lookup even if the base lookup flag isn't set). The only call that sets
this option is the XAddLocalChanAlias RPC endpoint, where we want to
make sure that a reverse lookup is stored in the alias manager in order
to later expose it via the new RPC method.

lnd: update docs on nodeann addresses retaining

brontide: add new maxMessageSize variable

brontide: use a static buffer for the packet length

In this commit, we eliminate the final allocation that takes place when
we write out messages. Once again this was escaping to the heap, so we
make it an attribute on the Machine struct, which allows pure static
allocation.

```
goos: darwin
goarch: arm64
pkg: github.com/lightningnetwork/lnd/brontide
cpu: Apple M4 Max
BenchmarkWriteMessage-16 25840 46376 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25646 46672 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25874 46391 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25512 46427 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25760 46309 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25789 46520 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25602 46619 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25766 46464 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25820 46487 ns/op 2 B/op 0 allocs/op
BenchmarkWriteMessage-16 25634 46553 ns/op 2 B/op 0 allocs/op
PASS
ok github.com/lightningnetwork/lnd/brontide 16.907s
```

docs: add docs explaining usage of pprof+benchmarks to optimize

In this commit, we add some docs that explain how to use tools like
heap escape analysis and memory profiling to fully eliminate allocations
in a sample program.

This guide is meant to help devs/contributors use Go's excellent perf
tools to zoom in on an optimization problem.

brontide+peer: use internal sync/pool to reduce allocations

This ensures that under medium to high load, we eliminate all
allocations once we arrive a steady state, re working memory.

brontide: use a fixed size buffer for the nonce within the brontide machine

In this commit, we use a fixed sized buffer for the nonce when we
read/write messages. This was actually escaping to the heap. We can
avoid this by statically allocating it alongside the struct itself.

The benchmark state at this point:

```
goos: darwin
goarch: arm64
pkg: github.com/lightningnetwork/lnd/brontide
cpu: Apple M4 Max
BenchmarkWriteMessage-16 25264 47012 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 23542 46809 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 25989 47256 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 25542 46388 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 26083 46612 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 25860 46367 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 24967 46748 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 26088 46485 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 25561 46425 ns/op 4 B/op 1 allocs/op
BenchmarkWriteMessage-16 25474 47249 ns/op 4 B/op 1 allocs/op
PASS
ok github.com/lightningnetwork/lnd/brontide 16.911s
```

```
goos: darwin
goarch: arm64
pkg: github.com/lightningnetwork/lnd/brontide
cpu: Apple M4 Max
│ old.txt │ new2.txt │
│ sec/op │ sec/op vs base │
WriteMessage-16 50.34µ ± 1% 46.68µ ± 1% -7.28% (p=0.000 n=10)

│ old.txt │ new2.txt │
│ B/op │ B/op vs base │
WriteMessage-16 73788.000 ± 0% 4.000 ± 0% -99.99% (p=0.000 n=10)

│ old.txt │ new2.txt │
│ allocs/op │ allocs/op vs base │
WriteMessage-16 5.000 ± 0% 1.000 ± 0% -80.00% (p=0.000 n=10)
```

brontide: add benchark for WriteMessage

In this commit, we add a benchmark for the WriteMessage method. This is
the first step in an upcoming optimizooor series of commits.

The baseline is:
```
goos: darwin
goarch: arm64
pkg: github.com/lightningnetwork/lnd/brontide
cpu: Apple M4 Max
BenchmarkWriteMessage-16 22736 50667 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 23217 50463 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 24241 49941 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 23574 51021 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 23784 49926 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 24230 50538 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 24058 49971 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 23762 50224 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 24266 53034 ns/op 73788 B/op 5 allocs/op
BenchmarkWriteMessage-16 23317 50045 ns/op 73788 B/op 5 allocs/op
PASS
ok github.com/lightningnetwork/lnd/brontide 17.433s
```

lnd: use persisted addrs if not set in config

lnd: stop using prev persisted addresses

In this commit we stop using persisted address in LND's prev run.
This means addresses set using `externalip` will be used without
merging them with the ones from prev run. We will introduce the
condition to use persisted addresses in the next commit.

itest: check for config addrs precedence

In this commit, we update the itest to check for precedence of the
config addresses over the persisted addresses.

We did not check for address persistence after restart (without the
extraArgs `--externalip`) because in `lntest/node/config.goL300`,
`GenArg` by default sets the `--externalip` flag, which makes
the config addrs to always take precedence over the persisted
addrs, for the tests.

funding: notify aux negotiator on ChannelReady

We notify the aux channel negotiator that an established channel is now
ready to use.

docs: add release note

lnwallet: include peer pub key in aux chan state

In order to help external components to query the custom records of a
channel we need to expose the remote peer pub key. We could look-up
custom records based on the funding outpoint, but that relation is
established when receiving the ChannelReady message. The external
components may query the AuxChanState before that message is received,
so let's make sure the peer pub key is also available.

lnwire: update tests for init message

htlcswitch+peer: set and read aux custom records

This is the final step, we actually call the interface and either
provide or retrieve the custom features over the message. We also notify
the aux components when channel reestablish is received.

lnd: add AuxChannelNegotiator to AuxComponents

We now plug-in the aux channel negotiator to the server impl config. We
also provide it to the peer config as that's where it's needed in order
to inject custom records in the appropriate peer messages.

lnwire: add custom records to init

Before calling the new interface we first add the ability for the peer
message itself to encode the new data records.

lnwallet: introduce AuxChannelNegotiator interface

We introduce this new interface with the purpose of injecting and
handling custom records on the init message, and also notifying
external components when receiving the ChannelReady or
ChannelReestablish message.