fix(multiple): miscellanous fixes/enhancements

[wpbonelli]

• update commit-triggered CI to run on any branch starting with prefix ci-diagnose*
• fix Python usage in cross-platform CI jobs
  • python isn't aliased to Python3 on Mac when bash -l {0} is the default shell, causing Python2 to be used
  • use shell: bash -l {0} only as required for Micromamba, otherwise shell: bash
• fix default values for hnoflo and hdry introduced in update(plotting): added default masked values  #1610
  • correct hdry default from -1e-30 to -1e30
  • add defaults to BaseModel (fix notebook errors caused by None passed to numpy)
  • this caused the MODFLOW 6 nightly build to fail — maybe worth switching that repo's dependency to FloPy master branch or a published release so issues that get past this repo's develop CI don't break the nightly distribution?

[codecov]

Codecov Report

Merging #1614 (4500ff1) into develop (5a9bec2) will decrease coverage by 0.0%.
The diff coverage is 100.0%.

@@            Coverage Diff            @@
##           develop   #1614     +/-   ##
=========================================
- Coverage     72.7%   72.7%   -0.1%     
=========================================
  Files          251     251             
  Lines        54501   54501             
=========================================
- Hits         39671   39665      -6     
- Misses       14830   14836      +6     

Impacted Files	Coverage Δ
flopy/mbase.py	69.2% <100.0%> (ø)
flopy/plot/crosssection.py	66.4% <100.0%> (ø)
flopy/plot/map.py	84.2% <100.0%> (ø)
flopy/utils/get_modflow.py	64.0% <0.0%> (-1.5%)	⬇️