Ensure the sticky room changes if the tag changes
This fixes a case where a user accepts an invite, which causes a tag change, but the room stays stuck in the invites list. The tag change additionally gets swallowed when the user moves away, causing the room to get lost.
By moving it when we see it, potentially during a sticky room change itself (though extremely rare), we avoid having the room get lost in the wrong lists. A side effect of this is that accepting an invite puts it at the top of the tag it's going to (usually untagged), however this feels like the best option for the user.
A rare case of a tag change happening during a sticky room change is when a leave event comes in for the sticky room, but because it's come through as a tag change it can get swallowed. If it does get swallowed and the user clicks away, the tag change will happen when the room is re-introduced to the list (fake NewRoom event).
