Fix some type instabilities and other fixes

[DanielVandH]

• Fixes some issue with type instabilities
• Adds construct_polygon_hierarchy to the public API list (it was already intended to be there)
• All computations are now in the provided precision except for the triangle area and circumcenter which are done in Float64. A warning is given when a non-Float64 precision is given.
• Closes #118
• Redesigns the Polygon struct to have an is_circular field, avoiding the need for views
• Completely refactors validate_triangulation. Still only lives in the test files though. Maybe one day it can live inside the package itself incase users somehow have a use for it..
• Clean up the runtests.jl file, and make sure that the README/docs are fully tested
• Use Aqua and fix ambiguities
• Remove accidental piracy of minimum(::Nothing)
• Remove CI spam from method redefinitions
• Fix some issues with doc images and some typos
• Fix #109

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.58233% with 11 lines in your changes missing coverage. Please review.

Project coverage is 95.31%. Comparing base (6910c27) to head (8b63858).

Files	Patch %	Lines
src/data_structures/trees/bst.jl	55.55%	4 Missing :warning:
src/geometric_primitives/boundary_nodes.jl	0.00%	2 Missing :warning:
src/algorithms/intersections/rtree.jl	50.00%	1 Missing :warning:
src/algorithms/triangulation/mesh_refinement.jl	94.44%	1 Missing :warning:
src/data_structures/trees/rtree.jl	88.88%	1 Missing :warning:
...structures/triangulation/methods/boundary_nodes.jl	80.00%	1 Missing :warning:
src/utils/utils.jl	83.33%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #119 +/- ## ========================================== + Coverage 95.06% 95.31% +0.25% ========================================== Files 92 92 Lines 9095 9145 +50 ========================================== + Hits 8646 8717 +71 + Misses 449 428 -21 ```

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