daemon: Don't leave dangling Action pointers in idle-time containers
Cherry-pick MR for !406 (merged).
If we delete the Action but don't clean up related map/set elements, the powerdevil daemon can crash e.g. in Core::onResumingFromIdle() and Core::onKIdleTimeoutReached().
This has been an issue since commit 584cfdf0 (or d91bc62f on 6.1) which made it possible for already-created actions to get deleted again at a later time.
(cherry picked from commit 7a929fa0)