Clean up structure/molecule aliases in ASE / MLFF jobs

[esoteric-ephemera]

Close #1353 by:

• Making structure and molecule properties that get populated by mol_or_struct in base ASE / MLFF docs
• Backwards compatibility: mol_or_struct gets populated by alias if structure or molecule is present
• Allow for removing mol_or_struct in ionic steps, and by specifying either mol_or_struct, molecule, or structure

[gpetretto]

Thanks @esoteric-ephemera for the fix! It looks good to me.

I just wanted to mention that the alias+property at the moment does not create any problem since in @forcefield_job no output_schema is defined. However, if this changes in the future, the following code can give an error:

job1=ForceFieldRelaxMaker(force_field_name="MACE_MP_0B3").make(s)
job2=ForceFieldRelaxMaker(force_field_name="MACE_MP_0B3").make(job1.output.output.structure)

AttributeError: OutputDoc does not have attribute 'structure'.

In light of this, I think it may be worth to update jobflow to handle cases like this. The change should be relatively small. What do you think @utf?

[esoteric-ephemera]

Thanks @gpetretto - we could move the structure attribute access over to mol_or_struct access instead. That would also make jobs / flows apply to molecules and structures simultaneously