Add moist Euler equations with test case

[benegee]

In the course of project ADAPTEX I would like to simulate the warm rising bubble test case in dry and moist air, described by Bryan and Fritsch (A Benchmark Simulation for Moist Nonhydrostatic Numerical Models, https://www.atmos.albany.edu/facstaff/rfovell/ATM562/bryan-fritsch-2002.pdf).

This has already been done by Lucas Gemein in his master's thesis, but was not merged into Trixi main.
His branch: https://github.com/NichtLucas/Trixi.jl/tree/thesis_gemein_2022
His PR: #1017
Oswald Knoth's PR: #171

ToDos:

• Dry air variant
  • Add LMARS flux in 2D: Add dry air warm bubble test case #1779
  • Add HLLC flux for non-cartesian meshes: HLLC flux for CEE on Non-Cartesian Grids #1741
  • Add elixir: Add dry air warm bubble test case #1779
• Moist air: Add moist Euler equations with warm bubble test case #1813
  • Can CompressibleEulerMulticomponentEquations2D be used or are separate equations needed?
  • Add missing fluxes to CompressibleEulerMulticomponentEquations2D
  • Add elixir

[DanielDoehring]

Possibly related: #171

[benegee]

Woohoo! Thanks for the hint. I had no idea how much stuff had already been around.

[DanielDoehring]

Regarding the HLLC flux for non-cartesian meshes: I have a issue on this #1692 where I show my attempt (which is unfortunately wrong, but I cannot find the bug :( )