feat(grb): support reading data strings from binary grid file

[mjreno]

MODFLOW-ORG/modflow6#1323
MODFLOW-ORG/modflow6#2254

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 76.0%. Comparing base (bb9824e) to head (378684f).
Report is 75 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/mf6/utils/binarygrid_util.py	50.0%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2478     +/-   ##
=========================================
+ Coverage     68.4%   76.0%   +7.6%     
=========================================
  Files          294     296      +2     
  Lines        59390   64051   +4661     
=========================================
+ Hits         40652   48742   +8090     
+ Misses       18738   15309   -3429     

Files with missing lines	Coverage Δ
flopy/mf6/utils/binarygrid_util.py	91.1% <50.0%> (-0.9%)	⬇️

... and 259 files with indirect coverage changes

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