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

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat commented:

I added some technical remarks in inline comments. If those are handled, I'm leaning towards merging this PR, because it I agree that these warnings (where the array would fit into the buffer where it's initialized, but the overhead of the array new can could technically cause issues) may be unwanted and confusing.

@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?

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