InterchangeOpenMMSolvationSettings is misleading since PackmolSolvationSettings also goes through Interchange #149
Description
Follow up from #140
So that they don't clash with the openfe settings of the same name, the OpenMM solvation settings were not called OpenMMSolvationSettings.
The word "Interchange" was added to reflect that we pre-calculate the number of waters using a manner similar to how the packmol interface in Interchange does it.
However, the PackmolSolvationSettings also do the same, ideally we would rename the settings to be similar. However, to avoid breaking API for SFEs, the PackmolSolvationSettings name was kept the same.
Long term we should refine these Settings names to something that is uniform acrross pontibus.