Differentiate the expire from leave event

At the moment we cannot see whether a user left a project due to their membership expiring or if they themselves opted to leave the project. This adds a new event type that allows us to make this differentiation. Note that is not really feasible to go back and reliably fix up the previous events. As a result the events for previous expire removals will remain the same however events of this nature going forward will be correctly represented.

Closes #22611 (closed)