[clang] [clang][Sema] Fix for enums overflowing (#24667) (PR #78742)

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wheatman wrote:

I believe I have correct implementations added for N3029 and N3030.  
I also tried to add tests.  One thing I was not sure about was how to add tests that have different expected behavior for different versions.  I just used  `#if __STDC_VERSION__  < 202311L` but please let me know if there is a better way.  I also updated the release notes to mention these additions.

https://github.com/llvm/llvm-project/pull/78742