Expose TreeMesh geometric intersections used for refine functions.

[jcapriot]

This PR unifies (and exposes) the geometric intersection tests used by the refine functionalities. The goal is to allow the user to see which cells actually intersected those geometric objects and use them to search for things.

This will expose operations to find cells that intersect with a

• Line (updated and fixes get_cells_along_line method not robust for tree mesh #346 )
• Box (updated)
• Ball
• Triangle
• Vertical Triangular Prism
• Tetrahedron
• Plane (which is a new addition to address MemoryError using mesh.plot_slice() with a TreeMesh of around 500,000 cells #355.)

It makes use of C++ templates and classes to reduce the repeated code for each of the different geometric objects.

[codecov]

Codecov Report

Attention: Patch coverage is 94.54545% with 24 lines in your changes missing coverage. Please review.

Project coverage is 86.04%. Comparing base (2cb2ff4) to head (cb802b5).
Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
discretize/mixins/mesh_io.py	52.00%	5 Missing and 7 partials ⚠️
discretize/tests.py	88.52%	3 Missing and 4 partials ⚠️
tests/base/test_volume_avg.py	97.50%	1 Missing and 1 partial ⚠️
discretize/tree_mesh.py	50.00%	1 Missing ⚠️
tests/tree/test_intersections.py	99.30%	0 Missing and 1 partial ⚠️
tests/tree/test_tree_io.py	97.72%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #356      +/-   ##
==========================================
+ Coverage   85.76%   86.04%   +0.27%     
==========================================
  Files          88       90       +2     
  Lines       18654    18461     -193     
  Branches     2959     2967       +8     
==========================================
- Hits        15998    15884     -114     
+ Misses       1996     1885     -111     
- Partials      660      692      +32     

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