testing overhaul, etc

[jGaboardi]

This PR:

• black formats repo (because somehow that never happened?)
• resolves nearly all warnings deprecation warnings in CI
  • see COMPAT: resolve matplotlib.cm warning in explore() geopandas/geopandas#2596
• converts testing infrastructure from unittest to pytest
• adds matching for specific warnings & errors and thrown messages from all that are currently tested against.
• other minor streamlines

[codecov]

Codecov Report

Merging #279 (0d7da9e) into main (1be809f) will increase coverage by 5.1%.
The diff coverage is 83.6%.

@@           Coverage Diff           @@
##            main    #279     +/-   ##
=======================================
+ Coverage   67.6%   72.6%   +5.1%     
=======================================
  Files         24      23      -1     
  Lines       2717    2387    -330     
  Branches     549     455     -94     
=======================================
- Hits        1836    1734    -102     
+ Misses       792     584    -208     
+ Partials      89      69     -20     

Impacted Files	Coverage Δ
spopt/BaseClass.py	52.6% <0.0%> (ø)
spopt/locate/base.py	95.0% <ø> (ø)
spopt/locate/p_dispersion.py	90.7% <ø> (ø)
spopt/region/azp.py	34.2% <ø> (ø)
spopt/region/spenc.py	100.0% <ø> (ø)
spopt/region/components.py	41.1% <33.3%> (ø)
spopt/region/objective_function.py	59.6% <33.3%> (ø)
spopt/region/base.py	91.2% <77.3%> (ø)
spopt/locate/coverage.py	99.0% <100.0%> (+<0.1%)	⬆️
spopt/locate/p_center.py	98.5% <100.0%> (+<0.1%)	⬆️
... and 7 more

[gegen07]

LGTM!