[Audiosharing] Check broadcast id instead of BIS for sink's receive state

In hysteresis mode, headset's BluetoothLeBroadcastReceiveState BIS Sync State could
change back and forth between 0, 1, 2, depending on broadcast playing
state. Thus BIS == 0 does not present that the sink has a valid source.
We check broadcast id in BluetoothLeBroadcastReceiveState instead.

Test: atest
Bug: 355222285
Flag: com.android.settingslib.flags.audio_sharing_hysteresis_mode_fix
Change-Id: Ie1f74d50872cd4a4285ea9dc9da8960706457dae