Add method to MED assistant class to allow passing object to retrieve property descriptors

TEIIDDES-1456 created a requirement to define both view and source model Extension Properties in the same MED but still need to filter what a user sees and can edit in the properties view.

native-query property on Procedures, applies to PHYSICAL model
non-prepared and deterministic properties applies to PHYSICAL model

For physial procedures with "is function == TRUE", the function extension properties need to get displayed for editing in properties view. So there needs to be some wiring/listening to refresh when properties changed or are originally loaded. Again, the Assistant class seems like the logic place to delegate the logic to.

By adding method to ModelExtensionAssistant class, ModelExtensionAssisantAggregator.getPropertyDefinitions(EObject) method could handle the filtering.