[FEAT] If possible check if AssertEdit available
[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

npdoty/pywikibot,TridevGuha/pywikibot-core,darthbhyrava/pywikibot-local,xZise/pywikibot-core,Darkdadaah/pywikibot-core,hasteur/g13bot_tools_new,PersianWikipedia/pywikibot-core,emijrp/pywikibot-core,happy5214/pywikibot-core,smalyshev/pywikibot-core,hasteur/g13bot_tools_new,Darkdadaah/pywikibot-core,icyflame/batman,wikimedia/pywikibot-core,trishnaguha/pywikibot-core,VcamX/pywikibot-core,magul/pywikibot-core,h4ck3rm1k3/pywikibot-core,npdoty/pywikibot,magul/pywikibot-core,hasteur/g13bot_tools_new,jayvdb/pywikibot-core,jayvdb/pywikibot-core,happy5214/pywikibot-core,wikimedia/pywikibot-core,h4ck3rm1k3/pywikibot-core,valhallasw/pywikibot-core