Add 3d subcell limiting example with nonconservative terms

[bennibolm]

Add 3d subcell limiting support for nonconservative terms of type NonConservativeSymmetric.

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 99.57983% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.86%. Comparing base (c2f9eb1) to head (eecc61b).

Files with missing lines	Patch %	Lines
src/equations/ideal_glm_mhd_3d.jl	97.96%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2688      +/-   ##
==========================================
+ Coverage   96.84%   96.86%   +0.02%     
==========================================
  Files         549      550       +1     
  Lines       43304    43539     +235     
==========================================
+ Hits        41935    42170     +235     
  Misses       1369     1369              

Flag	Coverage Δ
unittests	96.86% <99.58%> (+0.02%)	⬆️

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[DanielDoehring]

LGTM from software-engineering viewpoint