Do not allow `Drop` impl on foreign fundamental types
`Drop` should not be implemented on `Pin<T>` even if `T` is local.
This does not trigger regular orphan rules is because `Pin` is `#[fundamental]`... but we don't allow specialized `Drop` impls anyways, so these rules are not sufficient to prevent this impl on stable. Let's just choose even stricter rules, since we shouldn't be implementing `Drop` on a foreign ADT ever.
Fixes#99575
078844283c