When a range deletion task is waiting for ongoing queries to finish, such wait is independent from the executor the chain is scheduled on. As a result, invalidating the executor on stepdown does not cause the wait to end.

In order to don't leave dangling waits around, add a cancellation source member to the range deleter service that is initialized on step-up and invalidated on stepdown, then wait on the future with cancellation.

PS: if the ticket will be done after SERVER-68580, it will not be needed to provide a custom implementation of the cancellation source as it will already be available since the range deleter service is a replica set aware service.