Revert "Revert "Revert "[clang][UBSan] Add implicit conversion check for bitfields""" (#87562)

Reverts llvm/llvm-project#87529

Reverts #87518

https://lab.llvm.org/buildbot/#/builders/37/builds/33262 is still broken

GitOrigin-RevId: 029e1d751503268e3d8b01db769e710835c3010d
2 files changed