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
See merge request !6717
