[clang] [clang][NFC] Refactor expected directives in C++ DRs 1-99 (PR #73879)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

> I could nit on the naming conventions here or there, but I think this overall is such a vast improvement that I'd rather get 'this', then argue on names in future files, and let this one lie.

@erichkeane Now is the best time to bring those nits on, unless you want changes in C++ code (this is out of scope of this PR and my current efforts, which is focused on `expected` directives). I've been striking balance with both `-verify` prefixes naming and `#marker` names, so I'm very open to input on those names.

https://github.com/llvm/llvm-project/pull/73879