Update CarConnectionSummary

Per UX guidance, it's desired to always show the "disconnected" string
as the connected summary and to have a short summary option that simply
shows the "connected" string without any additional information.

Bug: 204943159
Test: make RunSettingsLibRoboTests
ROBOTEST_FILTER=com.android.settingslib.bluetooth.CachedBluetoothDeviceTest

Change-Id: I7744ceec534177bb6da8cd784e4cb3888f921f6f