Add parabolic BCs for P4estMesh{2}

[jlchan]

This PR adds parabolic boundary conditions for P4estMesh{2}. We added tests for non-periodic advection-diffusion on curved P4est meshes and the lid-driven cavity problem.

[codecov]

Codecov Report

Merging #1493 (28be493) into main (1b69182) will increase coverage by 0.06%.
The diff coverage is 97.81%.

@@            Coverage Diff             @@
##             main    #1493      +/-   ##
==========================================
+ Coverage   95.99%   96.04%   +0.06%     
==========================================
  Files         365      368       +3     
  Lines       30914    31049     +135     
==========================================
+ Hits        29673    29821     +148     
+ Misses       1241     1228      -13     

Flag	Coverage Δ
unittests	96.04% <97.81%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/solvers/dgsem_p4est/dg_2d_parabolic.jl	95.74% <94.00%> (+6.69%)	⬆️
...m/elixir_advection_diffusion_nonperiodic_curved.jl	100.00% <100.00%> (ø)
.../p4est_2d_dgsem/elixir_navierstokes_convergence.jl	100.00% <100.00%> (ø)
..._2d_dgsem/elixir_navierstokes_lid_driven_cavity.jl	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

[jlchan]

Bumping - @andrewwinters5000 would you have time for a quick review? @ranocha has gone over this PR once already.

[ranocha]

Looks good to me so far but I would like to get another review of @andrewwinters5000 (or someone else loving to look at curved code)

[andrewwinters5000]

There seems to be ambiguity of how flipped orientation interfaces are handled (although I only had a brief look at the implementation).

[andrewwinters5000]

LGTM!

[jlchan]

CI failures are unrelated and due to Plots.jl (see also #1548 and jheinen/GR.jl#522)