Restrict TreeMesh to hypercube domains

[patrickersing]

This fixes #1889

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.35%. Comparing base (f3e8878) to head (c288c3c).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2117   +/-   ##
=======================================
  Coverage   96.35%   96.35%           
=======================================
  Files         477      477           
  Lines       37751    37753    +2     
=======================================
+ Hits        36374    36376    +2     
  Misses       1377     1377           

Flag	Coverage Δ
unittests	96.35% <100.00%> (+<0.01%)	⬆️

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[ranocha]

Thanks

[patrickersing]

@ranocha shouldn't this be considered breaking? Elixirs that were setup with different domain lengths, will now throw an error.

[ranocha]

I consider this to be a bugfix

[ranocha]

The elixirs were not doing what they should have done anyway, so it's better to throw an error.