broadcaster: Introduce STOPPED audio state

This change introduces STOPPED audio state to cover blocking Audio
Framework calls of suspend, resume callbacks while broadcast is paused.

Bug: 349310336
Bug: 347204335
Flag: com.android.bluetooth.flags.leaudio_big_depends_on_audio_state
Test: atest bluetooth_test_broadcaster
Change-Id: Ifb1052d759eb739005ed4e1e8b1616458207ec58