move get components functionality?

[ijpulidos]

Currently we have the get_components functionality in the openmm_utils [sub]package. But it seems that this functionality is not really related to openmm. Rather, it is related to gufe, as far as I can tell.

I think it could be something that gufe could provide, see https://github.com/OpenFreeEnergy/gufe/issues/251

But in any case, it doesn't seem like something that should be in the openmm_utils space.