feat(arrays): add model.free_format_npl to control values-per-line in free-format array output

[reneangermeyer]

When FloPy writes free-format arrays for unstructured MODFLOW-USG models,
all values are written on a single line (e.g., 65,448 values on one line for
a large model). This makes files unreadable and difficult to diff or inspect.

Groundwater Vistas and other preprocessors write these same arrays with
10 values per line in block format, which is equally valid for MODFLOW but
far more readable.

This PR adds a model.free_format_npl property (values per line) that
controls line wrapping when writing free-format arrays.

Usage

m = flopy.mfusg.MfUsg.load('model.nam', model_ws='path')                                                                                                                      
m.free_format_npl = 10  # 10 values per line                                                                                                                                  
m.write_input()                                                                                                                                                               
                                                                                                                                                                              
Before (default, free_format_npl=None)                                                                                                                                        
                                                                                                                                                                              
INTERNAL 1 (FREE) -1                                                                                                                                                          
0.000000E+00  2.562436E-05  2.562436E-05  2.562436E-05  ...  (65,448 values on one line)                                                                                      
                                                                                                                                                                              
After (free_format_npl=10)                                                                                                                                                    
                                                                                                                                                                              
INTERNAL 1 (FREE) -1                                                                                                                                                          
0.000000E+00  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05                                    
2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05  2.562436E-05                                    
...                                                                                                                                                                           
                                                                                                                                                                              
Changes                                                                                                                                                                       
                                                                                                                                                                              
- mbase.py: add free_format_npl property (default None, no change in behavior)                                                                                                
- util_array.py: override npl in Util2d.string (INTERNAL arrays) and                                                                                                          
Util2d.get_file_entry (EXTERNAL/OPENCLOSE arrays) when property is set

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 72.3%. Comparing base (556c088) to head (cfe64e8).
⚠️ Report is 120 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/utils/util_array.py	83.3%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2696      +/-   ##
===========================================
+ Coverage     55.5%    72.3%   +16.8%     
===========================================
  Files          644      667      +23     
  Lines       124135   130408    +6273     
===========================================
+ Hits         68947    94390   +25443     
+ Misses       55188    36018   -19170     

Files with missing lines	Coverage Δ
flopy/mbase.py	70.4% <100.0%> (-2.3%)	⬇️
flopy/mfusg/mfusg.py	78.3% <ø> (+0.8%)	⬆️
flopy/modflow/mf.py	68.2% <ø> (-1.1%)	⬇️
flopy/utils/util_array.py	82.5% <83.3%> (-0.9%)	⬇️

... and 559 files with indirect coverage changes

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[wpbonelli]

seems good to me

[jdhughes-dev]

As is, this option will not be visible to anyone who does not know it exists. It could be pulled out as a kwarg and added to the docstring for the kwargs in mbase.

Also, there is no test(s) with evaluation that it is working as intended...although I don't think this is critical.

[jdhughes-dev]

Would simplify to

...block-format output, improving...

[reneangermeyer]

Simplified!

[jlarsen-usgs]

@reneangermeyer,
Just as a follow up to increasing the visibility of this option, it'd also make sense to explicitly define this option in the MfUsg class initialization parameters. As it is right now, it's still hidden from the end-user as a keyword argument that's not visible in the child class (MfUsg), even though it's explicitly defined in the parent (BaseModel) class.

[jlarsen-usgs]

Thanks for adding the keyword argument to the MfUsg Class. Overall, the changes look good to me.