[Task Manager] Clear smart launcher data when launcher URL changes

Task Manager occasionally re-uses task manager delegates, so the launcher URL can change during the lifetime of the object.
I already take care of this by resetting the storageId but I did not clear any badge or progress we might still have,
leading to wrong or random apps showing a badge that won't go away.

Differential Revision: https://phabricator.kde.org/D9839