[clang][UBSan] Add implicit conversion check for bitfields (#75481)

This patch implements the implicit truncation and implicit sign change
checks for bitfields using UBSan. E.g.,
`-fsanitize=implicit-bitfield-truncation` and
`-fsanitize=implicit-bitfield-sign-change`.

GitOrigin-RevId: 450f1952aced87584a53485d1ba1c2f77c3835a1
2 files changed