Bitcoin Core

index: shrink txospenderindex value markers

`TxoSpenderIndex` uses LevelDB values only as presence markers. `FindSpender` iterates over keys and loads the spending transaction from the disk position stored in each key.
Write new entries with a zero-byte span instead of a serialized empty string, so rebuilt indexes avoid one extra byte per spender entry.
Existing indexes remain readable because the lookup path does not deserialize the marker value.

test: return full keypair from `getnewdestination` helper

This can be useful for spending funds that are received at the created
address. Preparatory for the next commit, which modifies the taproot
functional test to work without the Bitcoin Core wallet compiled in.

private broadcast: limit outstanding txs to count of 10,000

Add a belt-and-suspenders feature, limit the amount of
memory and cpu possible when unlucky or simply misconfigured.
The worst case limit is roughly 400kB * 10,000 = 4GB, regardless
of usage pattern.

Before this change, sheer volume of broadcasts, mismatches in
standardness rules, or simply fee mismatches may result in unbounded
growth of memory usage. As the feature may be expanded in
the future, explicit bounds helps reasoning going forward.

doc: add release notes

bitcoin-util: Add netmagic command

test: ensure HTTPServer race condition is fixed

The result of WriteReply() losing the race condition would prevent any
new requests being read from the socket. The socket error test
sent 3 requests all at once after connecting, so in this commit
we separate the the third request to make the losing race
condition more likely, and make its effect more obvious.

http: prevent race condition between worker thread and I/O thread

This prevents a losing race condition that could prevent the server
from reading requests from an HTTP client.

A connected socket can either be written to or read from based on the
result of GenerateWaitSockets(). That method checks the HTTPRemoteClient
flag m_send_ready. If it's `true` the implication is that there is
data in the client's send buffer ready to go. Once that data is sent
and the buffer is empty, MaybeSendBytesFromBuffer() sets it `false` again.

The sad case was when a worker thread calling WriteReply() adds
data to the send buffer, but before it sets m_send_ready to `true`,
the I/O thread sends that data and empties the buffer. With the
buffer unexpectedly empty, WriteReply() sets m_send_ready to `true`.

The effect of this is that the socket will stay in "write" mode
with nothing to write. With nothing to write, MaybeSendBytesFromBuffer()
never sets it back to `false` and the socket is stuck forever.

depends: add openbsd_LDFLAGS

wallet: Replace CWalletTx's vOrderForm with specific fields

vOrderForm contained 2 kinds of strings: BIP 21 messages, and BIP 70
Payment Requests. Instead of having both inside of a single vOrderForm
field that is opaque, split them into separate std::vector<std::string>
to contain this metadata.

wallet: Drop vOrderForm from CommitTransaction

This parameter is only used to pass in the "Messages" from the GUI.
Instead of making it opaque by putting those into vOrderForm, use a
specific dedicated parameter for providing the messages.

script: qa: Improve Key::Fingerprint type safety

wallet: remove experimental warning from send RPCs

test: slow down rescaning process

wallet: Throw if unknown entry is found in mapValue

We know what entries are expected to be found in mapValue. If we
encounter one that is not recognized, then we should throw and refuse to
load the wallet in order to avoid losing user data once mapValue is no
longer used.

wallet: Drop mapValue from CWalletTx

It doesn't make sense to be storing relevant metadata variables inside
of a string map in CWalletTx. All of the fields have been pulled out
into separate members, so there is no need for mapValue to stick around.

wallet: Make CWalletTx "replaces_txid" and "replaced_by_txid" member variables

Instead of storing "replaces_txid" and "replaced_by_txid" as strings inside of
mapValue, store these expliclty as members of CWalletTx.

wallet: Make CWalletTx "comment" and "to" member variables

Instead of storing "comment" and "to" inside of mapValue, store these
expliclty as members of CWalletTx.

wallet: Make CWalletTx "from" and "message" member variables

Instead of storing "from" and "message" inside of mapValue, store these
explicitly as members of CWalletTx.

wallet: Pass comment and comment_to to CommitTransaction

Instead of passing these by setting them in mapValue, pass them directly
to CommitTransaction.

This is preparation for removing mapValue.

wallet: Drop mapValue from CommitTransaction

The values previously passed in mapValue are now parameters to
CommitTransaction so there is no need for mapValue to be passed.

wallet: Pass replaces_txid to CommitTransaction outside of mapValue

Instead of updating mapValue with the "replaces_txid" value and passing
the updated mapValue to CommitTransaction, pass the replaces_txid
directly to CommitTransaction which updates mapValue as necessary.

This is prepration for removing mapValue.

test: use ExtendedPrivateKey in wallet_taproot.py

test: use ExtendedPrivateKey in wallet_createwallet.py

test: use ExtendedPrivateKey in wallet_fundrawtransaction.py

test: use ExtendedPrivateKey in wallet_keypool.py