Re-enable isort and run on codebase

[nathanjmcdougall]

At the moment, isort isn't running because of the --diff option which effectively turns it into a print-only tool. The pre-commit doesn't actually print anything though, and it doesn't raise any exit code so the pre-commit, CI etc. will pass even when the tool thinks things are unsorted.

Similar to #1292, I suggest moving the configuration out of the pre-commit config file (and also setup.cfg) and into pyproject.toml.

I've run isort across the entire codebase, so a lot of files have changed (only cosmetically, of course).

[codecov[bot]]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (7a20c7a) 94.28% compared to head (006dafa) 77.13%.

Files	Patch %	Lines
pandera/pyspark.py	0.00%	3 Missing :warning:
pandera/typing/pandas.py	60.00%	2 Missing :warning:
pandera/api/pyspark/container.py	0.00%	1 Missing :warning:
pandera/backends/pyspark/column.py	0.00%	1 Missing :warning:
pandera/backends/pyspark/components.py	0.00%	1 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1295       +/-   ##
===========================================
- Coverage   94.28%   77.13%   -17.15%     
===========================================
  Files          91       91               
  Lines        7013     7011        -2     
===========================================
- Hits         6612     5408     -1204     
- Misses        401     1603     +1202     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[cosmicBboy]

hey @nathanjmcdougall would you mind taking a look at some of the merge conflicts? Not sure what was added/reordered by isort

[nathanjmcdougall]

@cosmicBboy I've taken a look - unfortunately seems there's an issue with attribute access in one of the doctests - as far as I can tell this is unrelated.