0.9.0 staging

[jcapriot]

Staging PR for 0.9.0 This changes all of the future warnings to errors, forcing users to update their code (and telling them how). All of these messages will be removed in the 1.0.0 future release when the entire repository gets cleaned up.

[codecov]

Codecov Report

Merging #323 (833ba7f) into main (bfb9237) will decrease coverage by 0.55%.
The diff coverage is 31.50%.

@@            Coverage Diff             @@
##             main     #323      +/-   ##
==========================================
- Coverage   85.70%   85.15%   -0.55%     
==========================================
  Files          38       38              
  Lines       11581    11535      -46     
==========================================
- Hits         9925     9823     -102     
- Misses       1656     1712      +56     

Impacted Files	Coverage Δ
discretize/View.py	0.00% <ø> (ø)
discretize/curvilinear_mesh.py	96.89% <ø> (ø)
discretize/mixins/mesh_io.py	90.03% <0.00%> (-0.84%)	⬇️
discretize/mixins/vtk_mod.py	88.21% <ø> (-0.55%)	⬇️
discretize/operators/differential_operators.py	78.66% <ø> (-2.35%)	⬇️
discretize/operators/inner_products.py	91.01% <0.00%> (-2.28%)	⬇️
discretize/tensor_mesh.py	81.89% <ø> (ø)
discretize/utils/codeutils.py	0.00% <0.00%> (ø)
discretize/utils/coordinate_utils.py	77.77% <ø> (ø)
discretize/utils/coordutils.py	0.00% <0.00%> (ø)
... and 18 more