prefer `functools.cached_property` for python >= 3.8

[jorenham]

and removed the required dependency on property_cached, since it's optional, and only required for Python 3.7

[jorenham]

This furthermore resolves a deprecation warning for pkg_resources on Python 3.11, caused by the import property_cached

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (778e203) 99.43% compared to head (d027688) 99.43%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #649 +/- ## ======================================= Coverage 99.43% 99.43% ======================================= Files 75 75 Lines 15452 15452 Branches 2087 2087 ======================================= Hits 15364 15364 Misses 63 63 Partials 25 25 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[jorenham]

I can't imagine that the failing test on python 3.9 has anything to do with the changes here. I'm guessing it's just flaky?

[bashtage]

Seems fine. Strange failure happens without this patch.

[bashtage]

Thanks.