fix(mp7particledata): add global_xy to to_prp

[dbrakenhoff]

• default is False which converts vertices to model coordinates
• add simple test

Note: method does get slow when it has to do the vertices conversion for lots of points. This can undoubtedly be optimized by first computing vertices in model coordinates or something along those lines. But I figured that was outside the scope for this PR.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 76.4%. Comparing base (bb9824e) to head (b9ce6b0).
Report is 26 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/modpath/mp7particledata.py	80.0%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2405     +/-   ##
=========================================
+ Coverage     68.4%   76.4%   +7.9%     
=========================================
  Files          294     294             
  Lines        59390   59712    +322     
=========================================
+ Hits         40652   45624   +4972     
+ Misses       18738   14088   -4650     

Files with missing lines	Coverage Δ
flopy/modpath/mp7particledata.py	88.4% <80.0%> (-0.5%)	⬇️

... and 245 files with indirect coverage changes

[wpbonelli]

Thanks for this