Unbind from service on app killed and dedup association requests

1. Listen to calling package binder death stopping the scanning on that.
2. Don't restart scanning when a request with the same values was made.

Bug: 30932767
Test: 1.:
  - Using a test app start scanning and kill the app.
  - In debug mode ensure that DeviceDiscoveryService#stopScan gets triggered
2.:
  - Start scanning and rotate the device while device chooser is visible
  - Ensure no visible loss of state is happening
Change-Id: If126a2c963da90172a956fbd88e6b3dcd7ac8b01