feat(PRT): add conversion/plotting utils for MF6 particle tracking mo…

…dels (#1753)

* to_coords() and to_prt() methods on particle data classes
* to_[mp7/prt]_[pathlines/endpoints]() conversion functions
* support plotting PRT pathlines in map/cross-section plots
* add basic tests for flopy.utils.geometry.point_in_polygon
* remove duplicate/parallel verts from voronoi grids (courtesy aprovost-usgs)
* work in progress, will evolve as mf6 PRT is developed

autotest/test_binaryfile.py

@@ -1,4 +1,3 @@
-import os
 from itertools import repeat
 
 import numpy as np
@@ -15,7 +14,6 @@
     CellBudgetFile,
     HeadFile,
     HeadUFile,
-    UcnFile,
     Util2d,
 )
 from flopy.utils.binaryfile import (