Refactor `HenrysLaw`

[K20shores]

Refactor HenrysLaw in musica.mechanism_configuration to use composition instead of inheritance from _HenrysLaw.

Acceptance Criteria

• The class no longer inherits from _HenrysLaw.
• The internal C++ instance is held in self._instance.
• All properties (name, gas_phase, gas_phase_species, aerosol_phase, aerosol_phase_water, aerosol_phase_species, other_properties) delegate to or update self._instance.
• gas_phase_species and aerosol_phase_species use Python Species or (float, Species) and convert to/from C++ _ReactionComponent.
• serialize() is converted from static method to instance method, operating only on Python-visible data.
• Public interface exposes only Python-native types with no direct C++ inheritance.

Ideas

• Follow the wrapper pattern from tuvx.py.
• Use helper functions or properties for clean conversion between Python and C++ types.
• Use @property decorators to forward attributes.
• Refactor serialize() as an instance method, removing static method usage.

Tasks

• Remove _HenrysLaw inheritance.
• Initialize self._instance as _HenrysLaw() inside __init__.
• Forward all attribute access and mutation to self._instance via properties.
• Convert gas_phase_species and aerosol_phase_species between Python and C++ representations on set/get.
• Refactor serialize() to instance method accessing Python-visible data only.
• Update call sites for serialization accordingly.