PERF: use from __future__ import annotations more
xref https://github.com/pandas-dev/pandas/pull/36034#issuecomment-684964511

@WillAyd using `python -X importtime -c "import pandas"` I don't see any different in import time after running a few times and things are cached.

so I don't think we gain anything from a performance POV and therefore only need to use it for stylistic reasons in a few modules and not across the codebase.

I've opened this PR, in case someone wants to test performance with these changes.

so feel free to close

Rather than do this in every module I think should just do where it actually makes a difference for annotations yep. that's my conclusion. feel free to close OK sure - can come back to this if that doesn't work out