feat(dis_properties): add grid method to get discretization properties

[jlarsen-usgs]

• returns dictionary of keyword arguments to build DIS, DISV, and DISU depending on grid type
• added cell .area calculation via shoelace algorithm to Grid
• remove deprecated flopy.mf6.utils/reference.py which housed "pre-modelgrid" spatial reference support for MF6 models

Mirrors support outlined in removed PR #2700

[codecov]

Codecov Report

❌ Patch coverage is 94.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.3%. Comparing base (556c088) to head (32a5609).
⚠️ Report is 197 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/discretization/unstructuredgrid.py	90.4%	2 Missing ⚠️
flopy/discretization/vertexgrid.py	83.3%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2795      +/-   ##
===========================================
+ Coverage     55.5%    73.3%   +17.7%     
===========================================
  Files          644      659      +15     
  Lines       124135   132157    +8022     
===========================================
+ Hits         68947    96913   +27966     
+ Misses       55188    35244   -19944     

Files with missing lines	Coverage Δ
flopy/discretization/grid.py	75.4% <100.0%> (-0.6%)	⬇️
flopy/discretization/structuredgrid.py	54.5% <100.0%> (+7.1%)	⬆️
flopy/utils/voronoi.py	81.6% <100.0%> (+12.2%)	⬆️
flopy/discretization/vertexgrid.py	80.1% <83.3%> (-3.6%)	⬇️
flopy/discretization/unstructuredgrid.py	83.1% <90.4%> (+1.6%)	⬆️

... and 580 files with indirect coverage changes

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[jlarsen-usgs]

PR will close
#2388
#2661

[jdhughes-dev]

The grid methods and the cell area calculation look good. I checked area against areas I could work out by hand and it is right for a structured grid with variable row and column spacing and for a vertex grid holding a square and a triangle.

Removing flopy/mf6/utils/reference.py is overdue. It was deprecated in 3.9 for removal in 3.10+, we are at 3.11, and nothing in flopy imports it.

Two things before this goes in:

• .docs/code.rst still lists ./source/flopy.mf6.utils.reference.rst. The files under source/ are written by sphinx-apidoc at build time, so once the module is gone that line points at a document that is never generated. Read the Docs is not set to fail on warnings and the docs are not built on a pull request, so this will not turn up until after the merge.
• Patch coverage is 55%, mostly the new get_dis*_kwargs paths.

Should this go in the release that accompanies MODFLOW 6 6.8.0, or wait for the one after?

[jlarsen-usgs]

@jdhughes-dev

I'll work on some additional testing and clean up the docs for the removed reference.py module.

There isn't a big rush to get this one in, so feel free to move forward with the release if this PR isn't completed in time.

[wpbonelli]

@jlarsen-usgs CI errors are unrelated and have been fixed separately, don't let them keep you from merging. In any case we won't be ready for the release for another few days yet.