ImageGalleryBase::factory does not have proper service injection for itself and the possible sub classes. Could use ObjectFactory for the subclasses

Should handle the fallback in exception case as seen in parser and some other locations.

Not sure if T145836 should be revisit while doing this.

https://codesearch.wmcloud.org/search/?q=ImageGalleryBase%3A%3Afactory&i=nope&files=&repos=

The function is used by the Parser (which is a service) and by some special pages (which are created by a service - T259960)