[clang] [Clang][Sema] placement new initializes typedef array with correct size (PR #83124)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

Can you explain which cases the `if (!ArraySize)` condition was catching before and why the change does not effect those cases? My fear is that we are breaking other cases but we don't have test coverage for those cases and we are missing those breaks.

https://github.com/llvm/llvm-project/pull/83124