Add moist Euler equations with test case

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:

- [x] Dry air variant
- [x] Add LMARS flux in 2D: #1779
- [x] Add HLLC flux for non-cartesian meshes: #1741
- [x] Add elixir: #1779
- [ ] Moist air: #1813
- [x] Can CompressibleEulerMulticomponentEquations2D be used or are separate equations needed?
- [ ] Add missing fluxes to CompressibleEulerMulticomponentEquations2D
- [ ] Add elixir