[clang] [Clang] Improve diagnostics for 'placement new' with const storage argument (PR #144270)

[Baranov Victor via cfe-commits]

vbvictor wrote:

Failed "[Test documentation build](https://github.com/llvm/llvm-project/actions/runs/15665481196/job/44129065574?pr=144270)" also fails without my commit, so it is unrelated

https://github.com/llvm/llvm-project/pull/144270