[clang] [llvm] [Coverage][MC/DC] Show uncoverable and unreachable conditions (PR #94137)

[via cfe-commits]

Lambdaris wrote:

Renamed the test to `mcdc-exclude` and add a test to check `--mcdc-exclude=none`
> So the default preserves existing behavior?

Yeah, existing behavior is equivalent to `--mcdc-exclude=constant` as default.

https://github.com/llvm/llvm-project/pull/94137