Teach st.from_type() about remaining generic types

[Zac-HD]

While working through the list of types in PEP 585 for #2653, I discovered some generic types that we don't currently have registered strategies for. While they're rarely used and nobody has every complained, it would be nice to add them! Note that this applies to every version of Python we support via the typing module equivalents; they're not new in 3.9.

master...Zac-HD:register-more-types has my current progress. Still to do:

• work out how dict_items is added to the strategy for collections.abc.Set[T] (which breaks because the elements are tuples, not the requested type), and stop that.
• write tests against the typing module versions which work on all supported Pythons.
• get collections.abc.Generator working.

Coroutine, AsyncGenerator, and contextlib.AbstractAsyncContextManager are hereby ruled out of scope though, since (a) nobody has asked for them and (b) testing them would be a complete pain because we don't currently have any async tests (see here for how that would work).