[clang] [clang][analyzer] Move checker alpha.unix.StdCLibraryFunctions out of alpha. (PR #66207)

[Balazs Benics via cfe-commits]

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

I didn't spent much time on this, but I think it should be good.
Please check the docs with Grammarly to catch mistakes.
Also, please generate the HTML for the rst to verify how it looks.

I'm not sure if the release docs mentions this, but it definitely should. Make sure that's the case.

I approve this, assuming that these wrinkles are ironed.

https://github.com/llvm/llvm-project/pull/66207