To offer the possibility to get information at plugin
level and get it from the registry, all the
full features are now registered in 'fullstaticfeatures'
meta plugin instead of NULL plugin.
In the case of gst-inspect, the features were not displayed
at plugin level because it was a NULL plugin.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5421>