Move ApiQueryRecentChanges::parseRCType to static method on RecentChange

Prior parseRCType was an private method in includes/api/ApiQueryRecentChanges and also
duplicated in includes/api/ApiQueryWatchList. This method has been made static and moved
to includes/changes/RecentChange.php.

Bug: 65071
Change-Id: Ic911fbcf9411c782685c4f956f8522051f2517f0
Merge "Move ApiQueryRecentChanges::parseRCType to static method on RecentChange"