[clang] [clang][NFC] Replace TypeAlignment with alignof(T) (PR #69185)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

It's in our public headers, and downstream users were supposed to rely on it, because `alignof` for `Type` and all its derived types reported the wrong value. So while I agree with you, I lean towards it being a breaking change which should be handled appropriately.

https://github.com/llvm/llvm-project/pull/69185