List object subclasses in the API reference

### Description of the modifications

In the legacy documentation on the STK devkit help, interfaces included references to classes that implement it. For example, the legacy base propagator interface, IAgVePropagator, has a list of coclasses that implement this interface. But, on the new docs, there is no such equivalent. This makes it difficult for a user to understand 'where to go' when an IPropagator interface is returned (for example, starting from the Satellite class docs and trying to make modifications to the propagator).

### Useful links and references

Legacy help example: https://help.agi.com/stkdevkit/#DocX/STKObjects~IAgVePropagator.html

Start by reviewing the new API reference for interface pages such as IPropagator and comparing it with the linked legacy IAgVePropagator example. Trace how the Satellite documentation exposes its propagator interface. Done means the relevant interface reference lists the object subclasses or implementing classes users can navigate to.

Written by the indexing model from the issue text.