core#21992

Remove -feefilter option

Feefilter option is debug only and it isn't used in any tests, it's wasteful
to check this option for every peer on every iteration of the message handler
loop. refs core#21545

Factor feefilter logic out

Break SendMessages() function into smaller units to improve readability.
Adds lock assert, as round() isn't thread safe.
closes #21545

core#24427

refactor: Release cs_main before MaybeSendFeefilter

This is a backport of core#21992 and core#24427
Depends on D12182

With Debug clang and tsan
ninja all check check-functional