[clang] [analyzer] Fix FP for cplusplus.placement new #149240 (PR #150161)

[Balazs Benics via cfe-commits]

https://github.com/steakhal requested changes to this pull request.

> @steakhal What do you think, which would be the better: merging this PR or preserving the counter-intuitive bug reports that warn about potential unusual behavior of array placement new?

The PR looks good. I don't think we would ever want the diagnostics we are about to drop in this PR.

https://github.com/llvm/llvm-project/pull/150161