broadcaster: Add passing broadcast metadata from native

This change exposes the local broadcast metadata to the application.
It is needed to use our local broadcast information in the
Broadcast Scan Assistant service and possibly present more
information on the ongoing broadcast itself.

Bug: 150670922
Tag: #feature
Test: atest BluetoothInstrumentationTests bluetooth_test_broadcaster_sm bluetooth_test_broadcaster
Sponsor: jpawlowski@
Change-Id: If47a63501dfa11ebca2e9b3937d7a1a1a4e7036c