[clang] Reapply "[Clang][Sema] placement new initializes typedef array with correct size (#83124)" (PR #89036)

[Pranav Kant via cfe-commits]

pranavk wrote:

@mahtohappy can we please revert this in the meantime while you look for a fix here. Feel free to land it again with the fix. 

https://github.com/llvm/llvm-project/pull/89036