Inline data sources not added to the registry fields

[achals]

Expected Behavior

If I create a feature view with an inline data source, it should be added to the registry and discoverable via feature_store.get_data_source.

Current Behavior

Only data sources defined as top level objects of the feature repo are stored and discoverable in the registry.

Possible Solution

In registry.py, introspect all feature views and collect them to be added to the registry.