[BT Broadcast Sink] Add the function for leave and scan QRcode buttons

Add function for 'leave broadcast' button
Add function for 'Scan QR code' button
Set 'level broadcast' button gray out when device does not have broadcast source

Bug: 228259065
Test: build pass and manually test
Change-Id: Iab4a45e73f49c3f755b95ea3fa38872daac7e745
2 files changed