[backport#15855] [refactor] interfaces: Add missing LockAnnotation for cs_main

Summary:
https://github.com/bitcoin/bitcoin/pull/15855/commits/fa3c6511435149782545ac0d09d4722dc115d709

Depends on D6260

Backport of Core PR15855

Test Plan:

cmake .. -GNinja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DENABLE_WERROR=ON -DENABLE_SANITIZERS=thread
ninja check-all
ninja
./src/bench/bitcoin-bench

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6259