Merge #19988: Overhaul transaction request logic

fd9a0060f028a4c01bd88f58777dea34bdcbafd1 Report and verify expirations (Pieter Wuille)
86f50ed10f66b5535f0162cf0026456a9e3f8963 Delete limitedmap as it is unused now (Pieter Wuille)
cc16fff3e476a9378d2176b3c1b83ad12b1b052a Make txid delay penalty also apply to fetches of orphan's parents (Pieter Wuille)
173a1d2d3f824b83777ac713e89bee69fd87692d Expedite removal of tx requests that are no longer needed (Pieter Wuille)
de11b0a4eff20da3e3ca52dc90948b5253d329c5 Reduce MAX_PEER_TX_ANNOUNCEMENTS for non-PF_RELAY peers (Pieter Wuille)
242d16477df1a024c7126bad23dde39cad217eca Change transaction request logic to use txrequest (Pieter Wuille)
5b03121d60527a193a84c339151481f9c9c1962b Add txrequest fuzz tests (Pieter Wuille)
3c7fe0e5a0ee1abf4dc263ae5310e68253c866e1 Add txrequest unit tests (Pieter Wuille)
da3b8fde03f2e8060bb7ff3bff17175dab85f0cd Add txrequest module (Pieter Wuille)

Pull request description:

  This replaces the transaction request logic with an encapsulated class that maintains all the state surrounding it. By keeping it stand alone, it can be easily tested (using included unit tests and fuzz tests).

  The major changes are:

  * Announcements from outbound (and whitelisted) peers are now always preferred over those from inbound peers. This used to be the case for the first request (by delaying the first request from inbound peers), and a bias afters. The 2s delay for requests from inbound peers still exists, but after that, if viable outbound peers remain for any given transaction, they will always be tried first.
  * No more hard cap of 100 in flight transactions per peer, as there is less need for it (memory usage is linear in the number of announcements, but independent from the number in flight, and CPU usage isn't affected by it). Furthermore, if only one peer announces a transaction, and it has over 100 in flight already, we still want to request it from them. The cap is replaced with a rule that announcements from such overloaded peers get an additional 2s delay (possibly combined with the existing 2s delays for inbound connections, and for txid peers when wtxid peers are available).
  * The limit of 100000 tracked announcements is reduced to 5000; this was excessive. This can be bypassed using the PF_RELAY permission (to accommodate locally dumping a batch of many transactions).

  This replaces #19184, rebased on #18044 and with many small changes.

ACKs for top commit:
  ariard:
    Code Review ACK fd9a006. I've reviewed the new TxRequestTracker, its integration in net_processing, unit/functional/fuzzing test coverage. I looked more for soundness of new specification rather than functional consistency with old transaction request logic.
  MarcoFalke:
    Approach ACK fd9a0060f028a4c01bd88f58777dea34bdcbafd1 🏹
  naumenkogs:
    Code Review ACK fd9a006. I've reviewed everything, mostly to see how this stuff works at the lower level (less documentation-wise, more implementation-wise), and to try breaking it with unexpected sequences of events.
  jnewbery:
    utACK fd9a0060f028a4c01bd88f58777dea34bdcbafd1
  jonatack:
    WIP light ACK fd9a0060f028a4c01bd88f58777dea34bdcbafd1 have read the code, verified that each commit is hygienic, e.g. debug build clean and tests green, and have been running a node on and off with this branch and grepping the net debug log. Am still unpacking the discussion hidden by GitHub by fetching it via the API and connecting the dots, storing notes and suggestions in a local branch; at this point none are blockers.
  ryanofsky:
    Light code review ACK fd9a0060f028a4c01bd88f58777dea34bdcbafd1, looking at txrequest implementation, unit test implementation, and net_processing integration, just trying to understand how it works and looking for anything potentially confusing in the implementation. Didn't look at functional tests or catch up on review discussion. Just a sanity check review focused on:

Tree-SHA512: ea7b52710371498b59d9c9cfb5230dd544fe9c6cb699e69178dea641646104f38a0b5ec7f5f0dbf1eb579b7ec25a31ea420593eff3b7556433daf92d4b0f0dd7

1 files changed, 9 insertions, 0 deletions

diff --git a/doc/release-notes-19988.md b/doc/release-notes-19988.md
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+P2P changes
+-----------
+
+The size of the set of transactions that peers have announced and we consider
+for requests has been reduced from 100000 to 5000 (per peer), and further
+announcements will be ignored when that limit is reached. If you need to
+dump (very) large batches of transactions, exceptions can be made for trusted
+peers using the "relay" network permission. For localhost for example it can
+be enabled using the command line option `-whitelist=relay@127.0.0.1`.