[clang] [clang] Add tests for some of CWG issues resolved in Croydon (2026-03) (PR #189299)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

> https://wg21.link/p4160r0 already works.

Indeed, I'll update the PR dse

> I think we can refer to it and update `cxx_dr_status.html` now.

Not yet, `make_cxx_dr_status` can't parse arbitrary papers. https://cplusplus.github.io/CWG/issues/cwg_index.html has to be brought up-to-date by CWG chair for this to happen.

https://github.com/llvm/llvm-project/pull/189299