[milanofthe]

Splitter moved to pathsim core (pathsim 0.29), GLC, Bubbler4 and IonisationChamber moved to pathsim-fusion (pathsim/pathsim-fusion#1).

• Removes the modules and their tests, they live in pathsim and pathsim-fusion now
• pathsim_chem and pathsim_chem.tritium keep the old names as deprecated aliases, resolved on access with a DeprecationWarning. They are re-exports and not listed in the namespace, so PathView does not register them twice
• Without pathsim-fusion installed, the fusion names raise an ImportError with pip install pathsim-fusion
• Requires pathsim>=0.29