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

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cor3ntin wrote:

> > @codemzs Any news? Thanks a lot for your work!
> 
> @cor3ntin Sorry for the delay, I plan to get back to this PR in the next few weeks. Do you need this change for something?
Nothing specific, I was just wondering sifting through PRs and our conformance page

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