fix(mnw1): fix mnw1 load

[jdhughes-dev]

• Fixed issue with stress_period_data when ITMP was < 1
• Added approach to read and write MNW1 add data after ITMP

[codecov]

Codecov Report

❌ Patch coverage is 86.36364% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.4%. Comparing base (556c088) to head (4850dc9).
⚠️ Report is 156 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/modflow/mfmnw1.py	84.2%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2752      +/-   ##
===========================================
+ Coverage     55.5%    72.4%   +16.8%     
===========================================
  Files          644      675      +31     
  Lines       124135   132100    +7965     
===========================================
+ Hits         68947    95684   +26737     
+ Misses       55188    36416   -18772     

Files with missing lines	Coverage Δ
flopy/utils/util_list.py	73.6% <100.0%> (-2.0%)	⬇️
flopy/modflow/mfmnw1.py	86.9% <84.2%> (-0.1%)	⬇️

... and 573 files with indirect coverage changes

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[wpbonelli]

looks like this supports a parameter in MNW1 that was not properly supported before

[jdhughes-dev]

looks like this supports a parameter in MNW1 that was not properly supported before

I ran into the issue trying to load the Denver Basin model. It did not read the stress period data correctly. Also it never did anything with the ADD variable in dataset 4 (which was not an issue with the Denver Basin model).

[wpbonelli]

@jdhughes-dev if you rebase I think this should pass. I replaced setup-micromamba with setup-pixi using the mf6 environments