Bluetooth: Use string in remote device summary

* Use String in connected device summary instead of resource id
* This allows dynamic strings to be built by CachedBluetoothDevice
  such as ones involve battery level percentages

Bug: 35874078
Test: make, unit test, test with Bluetooth devices
Change-Id: I583eac73280ca17387b215a4e7095e27de399998
5 files changed