[clang] [llvm] [MC/DC] Refactor: Introduce `ConditionIDs` as `std::array<2>` (PR #81221)

[NAKAMURA Takumi via cfe-commits]

chapuni wrote:

@evodius96 As an experiment, I've made subscripts as `bool`. It works semantically however I wonder they wouldn't be intuitive to us.

I can rewind it.

https://github.com/llvm/llvm-project/pull/81221