functools: Give up on lazy-importing types (#124736)

PR #121089 added an eager import for types.MethodType, but
still left the existing hacks for lazily importing from types.

We could also create MethodType internally in functools.py (e.g.,
by using `type(Placeholder.__repr__)`, but it feels not worth it at
this point, so instead I unlazified all the usages of types in the
module.