[clang] [Clang] [C23] Implement N2653: u8 strings are char8_t[] (PR #97208)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman approved this pull request.

LGTM, but please wait for @cor3ntin to give a final sign-off before landing.

https://github.com/llvm/llvm-project/pull/97208