net_processing: move extra transactions to msgproc mutex
Summary:
Previously vExtraTxnForCompact and vExtraTxnForCompactIt were protected by g_cs_orphans; protect them by g_msgproc_mutex instead, as they are only used during message processing.
Partial backport of core#26295:
https://github.com/bitcoin/bitcoin/pull/26295/commits/89e2e0da0bcd0b0757d7b42907e2d2214da9f68b
Depends on D16226.
Test Plan:
With Clang and Debug:
ninja all check ./contrib/teamcity/build-configurations.py build-tsan
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D16228