Also remove some superfluous map_ prefixes.

Thanks to Amin Timany for the suggestion.

Add both non-expansive and contractive functors, and bundle them for the general Iris instance as well as the global functor construction

This allows us to move the \later in the user-defined functor to any place we want.
In particular, we can now have "\later (iProp -> iProp)" in the ghost CMRA.

Since functor instances are just used as combinators, there is really
no need for functors that are not contractive.

make the global functor stuff in the various constructions more uniform; change it such that barrier/proof does not have to repeat the functors it needs

This cleans up some ad-hoc stuff and prepares for a generalization
of saved propositions.

I made the list of iFunctors monomorphic to avoid having to deal with
universe polymorphism, that is still somewhat flaky.