Add txrequest fuzz tests
Summary:
This adds a fuzz test that reimplements a naive reimplementation of TxRequestTracker (with up to 16 fixed peers and 16 fixed txhashes), and compares the real implementation against it.
Partial backport of core#19988:
https://github.com/bitcoin/bitcoin/pull/19988/commits/5b03121d60527a193a84c339151481f9c9c1962b
Depends on D9548.
Test Plan:
ninja bitcoin-fuzzers
Reviewers: #bitcoin_abc, majcosta
Reviewed By: #bitcoin_abc, majcosta
Differential Revision: https://reviews.bitcoinabc.org/D9549