[clang][Sema] Don't issue -Wcast-function-type-mismatch for enums with a...

[clang][Sema] Don't issue -Wcast-function-type-mismatch for enums with a matching underlying type (#87793)

Enums are passed as their underlying integral type so they're ABI compatible if the size matches.
Useful with C APIs that pass user-controlled values to callbacks that can be made type safe by using enumerations (e.g. GStreamer).

Discovered internally in some code after 999d4f84.