Make change tagging of edits in RecentChange::notifyNew/Edit

Change tags to apply to an edit can now be passed directly to the
WikiPage::doEditContent function. They are then passed to the
RecentChange::notifyNew/Edit functions where tagging is made
after the recent change is saved. This ensures that other callers
of doEditContent will not run into the same issue as T100248.
ApiRollback is fixed in this way.
In addition, we'll have to pass tags in this way for core tagging
of edits (I2e48bd458fc8d7c289f04dc276f9287516e0b987), and this makes
it possible to merge the arrays of tags and call ChangeTags::addTags
only once.

Change-Id: I829960c7a33b70464065839d7504d7529dfd0b72