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

This patch replaces usages of `TypeAlignment` with `alignof(T)`, where `T` is type that will be created in allocated storage with placement-new. This is now possible, because `alignof` reports the correct alignment for `Type` and classes derived from it after #68377 was merged.

While preparing #68377 I verified via `static_assert` that there are no mismatches of alignment between `TypeAlignment` and alignment of types derived from `Type`, so no changes are expected to codegen.