homogeneous nucleation of liquid droplets & expansion chamber example

[claresinger]

Copy/pasting the notes @slayoo added from our conversation with @AgnieszkaZaba this morning.

• the laboratory paper uses a Normal distribution rather than Lognormal - perhaps worth adding to PySDM
• a new ExpansionChamber environment (featuring perfect gas expansion, but not featuring hydrostatics) instead of using Parcel would help in making the code readable
• new adiabatic_exponent formulae
• a SuperParticleSpawningDynamic base-class could be best to derive from two dynamics: Seeding and HomogeneousLiquidNucleation
• rename SeedingMethods to shared SpawningMethods
• could we construct a simple adaptive substepping logic by comparing the nucleation rate and the timestep?
• test idea: J_homogeneous table from S&P
• test idea: long vs. short timestep
• test idea: S_max for short vs. long timestep
• test idea: conservation of total water
• test idea: check droplet number matches expectation from multiplicity of nucleated SDs

The expansion chamber example is aimed to mimic the laboratory experiments described here: https://arxiv.org/abs/2501.01467

[codecov]

Codecov Report

Attention: Patch coverage is 88.30409% with 20 lines in your changes missing coverage. Please review.

Project coverage is 85.24%. Comparing base (17cf24a) to head (7150f84).

Files with missing lines	Patch %	Lines
PySDM/environments/expansion_chamber.py	68.18%	14 Missing ⚠️
PySDM/environments/impl/moist_lagrangian.py	88.88%	2 Missing ⚠️
.../physics/adiabatic_exponent/moist_leading_terms.py	66.66%	2 Missing ⚠️
PySDM/dynamics/homogeneous_liquid_nucleation.py	96.42%	1 Missing ⚠️
PySDM/physics/adiabatic_exponent/dry.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #1492    +/-   ##
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  Coverage   85.24%   85.24%            
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  Files         379      389    +10     
  Lines        9297     9436   +139     
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+ Hits         7925     8044   +119     
- Misses       1372     1392    +20     

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