Merge bitcoin/bitcoin#32296: refactor: reenable implicit-integer-sign-change check for serialize.h

516f0689b5 refactor: re-enable UBSan implicit-sign-change in serialize.h (Lőrinc)
5827e93507 refactor: use consistent size type for serialization template parameters (Lőrinc)

Pull request description:

  Inspired by https://github.com/bitcoin/bitcoin/pull/32154, the main goal of this PR is to reenable sanitizer checks for `serialize.h` since it's modified in a few other PRs.

ACKs for top commit:
  maflcko:
    review ACK 516f0689b5 🎈
  stickies-v:
    ACK 516f0689b5, nice cleanup!

Tree-SHA512: 63da9bf1988a5b68e3c053b0ed786b8735f8f75b05763511522d1601b728b55798006e063137447615c266582622642d3226318fa83e488bd363f1756f8811e8

test/sanitizer_suppressions/ubsan

@@ -63,7 +63,6 @@ implicit-integer-sign-change:crypto/
 implicit-integer-sign-change:TxConfirmStats::removeTx
 implicit-integer-sign-change:verify_flags
 implicit-integer-sign-change:EvalScript
-implicit-integer-sign-change:serialize.h
 implicit-signed-integer-truncation:crypto/
 implicit-unsigned-integer-truncation:crypto/
 shift-base:arith_uint256.cpp