Make restraint objects `GufeTokenizable`

[jthorton]

Is your feature request related to a problem? Please describe.

We identified in the SepTop PR that it would be much nicer to obtain the BoreschRestraintGeometry from the protocol result when inspecting the restraints, rather than a list of dictionaries.

Describe the solution you'd like

Making the restraint geometry objects inherit from GufeTokenizable would allow this.

Describe alternatives you've considered

Additional context

[IAlibay]

Just correcting myself a bit, they probably don't have to be tokenizable, but they do have to be json serializable within the context of gufe, which last I checked they weren't.