[clang] [Clang] add emit -Wignored-base-class-qualifiers diagnostic for cv-qualified base classes (PR #132116)

[Erich Keane via cfe-commits]

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

I'm happy when Aaron is happy with commit message/etc.  THOUGH we should do `Fixes: #<BUG NUMBER>` in it so it auto-closes the bug.

I suspect we'll have to merge this for you, so if you notice CI has passed, feel free to ping us and we'll do it.

https://github.com/llvm/llvm-project/pull/132116