[mlir] Infer SubElementInterface implementations using the storage KeyTy

[mlir] Infer SubElementInterface implementations using the storage KeyTy

The KeyTy of attribute/type storage classes provide enough information for
automatically implementing the necessary sub element interface methods. This
removes the need for derived classes to do it themselves, which is both much
nicer and easier to handle certain invariants (e.g. null handling). In cases where
explicitly handling for parameter types is necessary, they can provide an implementation
of `AttrTypeSubElementHandler` to opt-in to support.

This tickles a few things alias wise, which annoyingly messes with tests that hard
code specific affine map numbers.

Differential Revision: https://reviews.llvm.org/D137374