[clang] [clang] Add tests for DRs about inheriting constructors (PR #79981)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

To be honest, I'm not keen on the idea of filing bug tracker issues for problems accounted for in other way (DR status, `FIXME`), until we get bug tracker in a good shape, or at least have an understanding how project management side of things is going to look.

> Is there anything in P0136R1 that would not be covered by these core issues?

I'm not sure what do you try to understand by asking this question, but the answer is likely "no".

https://github.com/llvm/llvm-project/pull/79981