When the sidecar is terminating because of SIGTERM, it should finish all running operations + release its leader election lease. This will allow another attacher sidecar to pick the lease quickly, without waiting for leader election timeouts.

"Finish all running operations" could be accomplished by cancelling a global context.Context +waiting for workqueues to finish.

This affects all sidecars, using the attacher to agree on a solution + a testable PR that can then be copied to all sidecars.