fix(plot): support plotting hfb packages

[wpbonelli]

Close #2676. Show HFBs in orange in map view and cross section plots. This needed functions to find a shared face given two adjacent cell numbers. We have a similar one in cvfdutil.py to find the shared face given cell vertices, but not given cell IDs.

Horizontal barriers are plotted as lines in map view and rectangular patches in cross section, vice versa for vertical barriers.

Map view, horizontal barrier

Map view, vertical barrier

Map view, horizontal and vertical barriers (note bold orange cell faces on the upper right)

Cross section, horizontal barrier

Cross section, horizontal and vertical barriers

[codecov]

Codecov Report

❌ Patch coverage is 79.38144% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.7%. Comparing base (556c088) to head (924c27e).
⚠️ Report is 104 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/plot/plotutil.py	54.3%	26 Missing ⚠️
flopy/plot/crosssection.py	88.7%	8 Missing ⚠️
flopy/plot/map.py	90.9%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2677      +/-   ##
===========================================
+ Coverage     55.5%    72.7%   +17.2%     
===========================================
  Files          644      667      +23     
  Lines       124135   130014    +5879     
===========================================
+ Hits         68947    94650   +25703     
+ Misses       55188    35364   -19824     

Files with missing lines	Coverage Δ
flopy/plot/map.py	81.5% <90.9%> (-0.6%)	⬇️
flopy/plot/crosssection.py	64.8% <88.7%> (-2.3%)	⬇️
flopy/plot/plotutil.py	51.4% <54.3%> (-5.5%)	⬇️

... and 552 files with indirect coverage changes

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