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
