feat(netcdf): support creating and loading model netcdf input files

[mjreno]

Initial support for NetCDF model utility classes:

• currently focused on input arrays (no timeseries)
• dependent on FloPy discretization classes
• support creating, loading and modifying grid associated array data
• create or load "layered mesh" (structured(DIS)/vertex(DISV)) or "structured" (structured(DIS)) format types
• creates files suitable as MODFLOW 6 inputs when dataset is associated with a MODFLOW 6 model
• integrated into mf6 core module: reads and writes MODFLOW 6 input files that follow NETCDF variable formats as described in the mf6io guide

[codecov]

Codecov Report

Attention: Patch coverage is 90.19074% with 72 lines in your changes missing coverage. Please review.

Project coverage is 76.0%. Comparing base (bb9824e) to head (5cc5b0a).
Report is 59 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/utils/model_netcdf.py	89.4%	64 Missing ⚠️
flopy/mf6/data/mfdataarray.py	89.2%	3 Missing ⚠️
flopy/mf6/mfmodel.py	94.8%	2 Missing ⚠️
flopy/mf6/mfpackage.py	83.3%	2 Missing ⚠️
flopy/mf6/data/mffileaccess.py	94.7%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2417     +/-   ##
=========================================
+ Coverage     68.4%   76.0%   +7.6%     
=========================================
  Files          294     294             
  Lines        59390   62635   +3245     
=========================================
+ Hits         40652   47646   +6994     
+ Misses       18738   14989   -3749     

Files with missing lines	Coverage Δ
flopy/mf6/data/mfdataplist.py	79.8% <100.0%> (+7.2%)	⬆️
flopy/mf6/data/mfdatastorage.py	75.7% <100.0%> (+6.8%)	⬆️
flopy/mf6/data/mfstructure.py	64.3% <100.0%> (+0.2%)	⬆️
flopy/mf6/mfsimbase.py	75.0% <100.0%> (+12.8%)	⬆️
flopy/mf6/utils/createpackages.py	6.4% <ø> (ø)
flopy/mf6/data/mffileaccess.py	76.2% <94.7%> (+5.2%)	⬆️
flopy/mf6/mfmodel.py	84.4% <94.8%> (+28.3%)	⬆️
flopy/mf6/mfpackage.py	82.1% <83.3%> (+17.4%)	⬆️
flopy/mf6/data/mfdataarray.py	68.2% <89.2%> (+9.6%)	⬆️
flopy/utils/model_netcdf.py	89.4% <89.4%> (ø)

... and 248 files with indirect coverage changes