p2p: Release m_peer_mutex early in InitiateTxBroadcastToAll #35297

The InitiateTxBroadcastToAll method holds the m_peer_mutex while updating the bloom filters for all peers. This is perfectly fine, because updating the bloom filters is fast. Though, from a style-perspective, the lock does not need to be held for the whole function. Also, holding the lock longer, may confuse Tsan into a lock-order inversion false-positive (ref: #19303 (comment)).

So "fix" both issues in this style-refactor.

<!--e57a25ab6845829454e8d69fc972939a-->

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

<!--006a51241073e994b41acfe9ec718e94-->

Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/35297.

<!--021abf342d371248e50ceaed478a90ca-->

Reviews

See the guideline for information on the review process.

If your review is incorrectly listed, please copy-paste <code>&lt;!--meta-tag:bot-skip--&gt;</code> into the comment that the bot should ignore.

<!--174a7506f384e20aa4161008e828411d-->

Conflicts

Reviewers, this pull request conflicts with the following ones:

• #34628 (p2p: Replace per-peer transaction rate-limiting with global rate limits by ajtowns)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

<!--5faf32d7da4f0f540f40219e4f7537a3-->

Code review ACK fa2afba28b5776a710386a3bacd5cb308149d671

While reviewing #34628 noticed this minor issue with m_peer_mutex being held for too long. The refactor looks clean to me.