custom-entities aren't able to work with select-tags

[Prashansa-K]

https://kongstrong.slack.com/archives/C04349E4KRC/p1741800926489459

Gateway doesn't support tags for degraphql_routes (and a lot of other custom_entities). So, select-tags in deck isn't able to filter them out.
If an associated service isn't a part of the selected configuration considered by deck via select-tags, we get errors in building state.

[mheap]

Can this be worked around using default_lookup_tags?