HLLC Flux for Ideal MHD 1D

[DanielDoehring]

This implements the HLLC flux for 1D MHD as proposed in https://doi.org/10.1016/j.jcp.2004.08.020 .

2D & 3D Versions for cartesian mashes will follow.

[github-actions]

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[ranocha]

It would be nice to get a review from @andrewwinters5000

[andrewwinters5000]

The new HLLC flux terms look okay and match the formulations given by Li. Although I am not sure the correct version of the SStar is used currently.

Also, when one goes to adapt this HLLC flux to multiple dimensions, some extra work will be required because there we will need to account for the cleaning variable $\psi$ and its associated "energy" $0.5\psi^2$ is the wave speed estimates.

[codecov]

Codecov Report

Attention: 31 lines in your changes are missing coverage. Please review.

Comparison is base (1b75f5e) 96.23% compared to head (8a766a8) 88.84%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1702      +/-   ##
==========================================
- Coverage   96.23%   88.84%   -7.39%     
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  Files         425      425              
  Lines       34253    34314      +61     
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- Hits        32960    30483    -2477     
- Misses       1293     3831    +2538     

Flag	Coverage Δ
unittests	88.84% <57.53%> (-7.39%)	⬇️

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

Files	Coverage Δ
src/equations/ideal_glm_mhd_1d.jl	91.14% <57.53%> (-8.86%)	⬇️

... and 50 files with indirect coverage changes

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[andrewwinters5000]

LGTM!