Alias namespace.availableFeatures to namespace.licensedFeatures

In %18.1, we introduced the namespace.licensedFeatures field in GQL. It was noted that since not all of the fields in the type are necessarily licensed features (e.g. has_issue_date_filter_feature), a more appropriate name would be namespace.availableFeatures.

Shared in (internal) slack:

I see. So this isn't really just for licensed features it could be related to any kind of feature availability. Maybe we could rename it to availableFeatures instead

We should consider renaming this field to prevent confusion.