[clang] [clang][NFC] Specify Type and ExtQuals as having 16-byte alignment (PR #68377)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

My plan is to phase-out `TypeAlignment` in subsequent patches, because we have proper language support for `alignas` and `alignof` now. It's the only one of its kind passed to `Allocate()` (I inspected all references to this function).
CC @zygolod as the author of ee0ce302c5eb4f26738f334f2fd8b165fa65dfca

https://github.com/llvm/llvm-project/pull/68377