update(Mf6Splitter): added split_multi_model method

[jlarsen-usgs]

• split_multi_model method allows splitting of connected GWF-GWT models
• update exchange remapping for GWT support

[codecov]

Codecov Report

Attention: Patch coverage is 19.23077% with 84 lines in your changes missing coverage. Please review.

Project coverage is 74.3%. Comparing base (9349a07) to head (7df5c7b).

Files with missing lines	Patch %	Lines
flopy/mf6/utils/model_splitter.py	19.2%	84 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2352     +/-   ##
=========================================
- Coverage     74.4%   74.3%   -0.1%     
=========================================
  Files          292     292             
  Lines        59526   59617     +91     
=========================================
+ Hits         44308   44325     +17     
- Misses       15218   15292     +74     

Files with missing lines	Coverage Δ
flopy/mf6/utils/model_splitter.py	67.4% <19.2%> (-3.1%)	⬇️

... and 3 files with indirect coverage changes

[mjr-deltares]

Hey @jlarsen-usgs , I looked at the failing test and realized I was having similar issues. The storage package is created with:

        ... 
        steady_state={0: True, 1: False},
        transient={0: False, 1: True},
    )

which the splitter can't process into something valid. Reducing it to:

    steady_state={0: True},
    transient={1 : True},
)

works as intended.

[jlarsen-usgs]

@mjr-deltares

Thanks for pointing this out. I was at a loss yesterday afternoon as to what the difference was, because it runs fine on windows. I'll look into this some more; I should be able to put together a fix for mapping those records to the split models.