GUI changes for best position angle feature / parallactic angle feature.

The following changes are UI only for OCSADV-23 and subtasks. The logic for best PA for guiding have yet to be completed.
Instead of a separate singleton and Map, maybe these should be added directly to the instruments themselves and the `validPosAngleConstraints` method added to the `PosAngleConstraintAware` interface?  Then there isn't a separate thing to remember to update.