MAINT: Modernize setup

[bashtage]

Move away from setup.py
Bump requirements
Update CI
Rerun black, isort, flake8

• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• passes black --check pandas_datareader

[codecov-commenter]

Codecov Report

Attention: 26 lines in your changes are missing coverage. Please review.

Comparison is base (fdade48) 73.19% compared to head (afb86ba) 58.48%.
Report is 25 commits behind head on main.

❗ Current head afb86ba differs from pull request most recent head e65293c. Consider uploading reports for the commit e65293c to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #978       +/-   ##
===========================================
- Coverage   73.19%   58.48%   -14.71%     
===========================================
  Files          65       65               
  Lines        2932     2929        -3     
  Branches      315      463      +148     
===========================================
- Hits         2146     1713      -433     
- Misses        704     1138      +434     
+ Partials       82       78        -4     

Files	Coverage Δ
pandas_datareader/__init__.py	35.00% <100.00%> (-5.91%)	⬇️
pandas_datareader/compat/__init__.py	70.27% <100.00%> (-19.21%)	⬇️
pandas_datareader/fred.py	100.00% <ø> (ø)
pandas_datareader/iex/__init__.py	63.41% <100.00%> (-9.76%)	⬇️
pandas_datareader/iex/stats.py	77.46% <ø> (-9.86%)	⬇️
pandas_datareader/tests/av/test_av_time_series.py	29.89% <ø> (ø)
pandas_datareader/tests/io/test_jsdmx.py	100.00% <ø> (ø)
pandas_datareader/tests/test_bankofcanada.py	100.00% <100.00%> (ø)
pandas_datareader/tests/test_base.py	100.00% <100.00%> (ø)
pandas_datareader/tests/test_fred.py	100.00% <100.00%> (ø)
... and 13 more

... and 16 files with indirect coverage changes

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