Remove interfaces and boundaries from cache_parabolic

[jlchan]

Addresses step 3 of #1674

[github-actions]

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[codecov]

Codecov Report

Attention: 24 lines in your changes are missing coverage. Please review.

Comparison is base (ad384c6) 96.27% compared to head (d93198d) 86.60%.

Files	Patch %	Lines
src/solvers/dgsem_tree/dg_1d_parabolic.jl	0.00%	20 Missing ⚠️
src/callbacks_step/amr_dg1d.jl	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1754      +/-   ##
==========================================
- Coverage   96.27%   86.60%   -9.67%     
==========================================
  Files         438      438              
  Lines       35623    35609      -14     
==========================================
- Hits        34294    30836    -3458     
- Misses       1329     4773    +3444     

Flag	Coverage Δ
unittests	86.60% <45.45%> (-9.67%)	⬇️

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[DanielDoehring]

@jlchan thanks for starting working on this! Sorry for not helping out on this, I thought (based on a comment during one of the Trixi meetings) that merging the 3D functionality would come first prior to addressing possible optimizations.

Anyways, feel free to ask for a review once you are done with the optimizations.

[jlchan]

Good point @DanielDoehring. We can merge 3D first and simply use this as a CI testing PR until then.

[DanielDoehring]

Having merged #1765 we can now turn our attention on this.