[FEAT] If possible check if AssertEdit available

Previously it assumed the AssertEdit extension is available, when
the extensions weren't cached yet. But because a siteinfo request
does not require an 'edit' action it should be safely possible
to always retrieve the extensions information and always determine
if it's installed or not.

Change-Id: I5ed6a9c4921f5b453eca1eaeae8aa03baa5645a1
Merge "[FEAT] If possible check if AssertEdit available"