This should prevent child fixtures from hubs breaking tests due to
missing discovery info. To get these devices in `filter_fixtures`
include protocol string of `SMART.CHILD`.
This is in preparation for tests based on supporting features amongst
other tweaks:
- Consolidates the filtering logic that was split across `filter_model`
and `filter_fixture`
- Allows filtering `dev` fixture by `component`
- Consolidates fixtures missing method warnings into one warning
- Does not raise exceptions from `FakeSmartTransport` for missing
methods (required for KS240)
