Add moist Euler equations with warm bubble test case

[benegee]

This PR restructures CompressibleEulerMulticomponentEquations

• AbstractCompressibleEulerMulticomponentEquations{2} is introduced as another abstract type. All common methods are implemented for this abstract type
• CompressibleEulerMulticomponentEquations{2} now is a subtype of AbstractCompressibleEulerMulticomponentEquations{2}. It holds the data (gammas, gas constants, ...) as before. Methods depending on that data are implemented for this type as before.
• CompressibleMoistEulerEquations2D is introduced as another subtype of CompressibleEulerMulticomponentEquations. Compared to CompressibleEulerMulticomponentEquations the latent head of vaporization is added. Methods needing to account for it are implemented for this type, possibly overriding common methods.

Also a test case is added.

Part of #1778

[github-actions[bot]]

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Testing

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Created with :heart: by the Trixi.jl community.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 43.40474% with 502 lines in your changes are missing coverage. Please review.

Project coverage is 91.60%. Comparing base (2dfde7f) to head (1e4e76d).

Files	Patch %	Lines
...ions/compressible_euler_multicomponent_moist_2d.jl	0.00%	195 Missing :warning:
...red_2d_dgsem/elixir_eulermultimoist_warm_bubble.jl	0.00%	165 Missing :warning:
...s/compressible_euler_multicomponent_abstract_2d.jl	79.91%	85 Missing :warning:
.../equations/compressible_euler_multicomponent_2d.jl	45.19%	57 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1813      +/-   ##
==========================================
- Coverage   96.30%   91.60%   -4.70%     
==========================================
  Files         439      442       +3     
  Lines       35749    36307     +558     
==========================================
- Hits        34428    33259    -1169     
- Misses       1321     3048    +1727     

Flag	Coverage Δ
unittests	91.60% <43.40%> (-4.70%)	:arrow_down:

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