[clang] [Clang][C++23] Core language changes from P1467R9 extended floating-point types and standard names. (PR #78503)

[M. Zeeshan Siddiqui via cfe-commits]

codemzs wrote:

@tahonermann @zahiraam I have migrated the review from https://reviews.llvm.org/D149573 here and have addressed your most recent comment. 

I'm not sure how to add you as reviewers as I don't see that option on my end.

https://github.com/llvm/llvm-project/pull/78503