[clang] [clang][NFC] Mark CWG2807 as implemented and add a test (PR #194755)

[Vlad Serebrennikov via cfe-commits]

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

For the context, this feature was also considered by WG21 a year ago in Hagenberg as [P3421](https://wg21.link/p3421) "Consteval destructors", which received a lot of... feedback from CWG.

https://github.com/llvm/llvm-project/pull/194755