Remove Devices from RemoteTaskStore when the transport is lost

* Update ConnectedAssociationStore to expose full information on an association, so RemoteTaskStore can retrieve the device name.
* Subscribe RemoteTaskStore to ConnectedAssociationStore
* Remove entries from RemoteTaskStore when the device disconnects, as notified by ConnectedAssociationStore.

Flag: android.companion.enable_task_continuity
Test: Added unit tests
Bug: 400970610
Change-Id: If8d91943937e7026ba23a8e7ac24fd4f03ed26bb