feat(get-modflow): support windows parallel nightly build

[wpbonelli]

• support installing parallel windows build with --repo modflow6-nightly-build --ostag win64par*
• ci(parallel): add parallel windows distribution MODFLOW-USGS/modflow6#1682

*maybe consider generalizing in future — instead of hardcoding supported asset names, dynamically discover them from the release info? in particular, if assets are expected to change as more mf6 variants (architecture, parallel/netcdf, etc) are included

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.1%. Comparing base (b142b08) to head (ffb18eb).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2128     +/-   ##
=========================================
+ Coverage     71.3%   73.1%   +1.7%     
=========================================
  Files          259     259             
  Lines        59511   59526     +15     
=========================================
+ Hits         42479   43531   +1052     
+ Misses       17032   15995   -1037     

Files	Coverage Δ
flopy/utils/get_modflow.py	64.2% <100.0%> (-0.1%)	⬇️

... and 59 files with indirect coverage changes