performance(to_geodataframe()): update GeoDataFrame construction routine

[jlarsen-usgs]

• 3x speedup initial GeoDataFrame construction time
• tested on 1,000,000 node grid
• Caching for about 100x speedup on repeated GeoDataFrame construction time

[codecov]

Codecov Report

❌ Patch coverage is 82.35294% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.3%. Comparing base (556c088) to head (bb04395).
⚠️ Report is 115 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/discretization/grid.py	83.3%	3 Missing ⚠️
flopy/discretization/structuredgrid.py	80.0%	1 Missing ⚠️
flopy/discretization/unstructuredgrid.py	80.0%	1 Missing ⚠️
flopy/discretization/vertexgrid.py	83.3%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2691      +/-   ##
===========================================
+ Coverage     55.5%    72.3%   +16.8%     
===========================================
  Files          644      667      +23     
  Lines       124135   130338    +6203     
===========================================
+ Hits         68947    94319   +25372     
+ Misses       55188    36019   -19169     

Files with missing lines	Coverage Δ
flopy/discretization/structuredgrid.py	53.8% <80.0%> (+6.3%)	⬆️
flopy/discretization/unstructuredgrid.py	81.0% <80.0%> (-0.5%)	⬇️
flopy/discretization/vertexgrid.py	80.0% <83.3%> (-3.7%)	⬇️
flopy/discretization/grid.py	74.4% <83.3%> (-1.6%)	⬇️

... and 559 files with indirect coverage changes

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