Refactor tests of geometry computations

[Eirik Keilegavlen]

Tests for pp.geometry

Tasks

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1. unit/test_distance_computations.py
2. unit/test_inside_polygon.py
3. unit/test_is_point_in_cell.py
4. unit/test_map_geometry.py
5. unit/test_match_triangles.py
6. unit/test_point_geometry_computations.py
7. unit/test_snap_points_to_lines.py
8. unit/test_ccw.py
9. unit/test_adtree.py