audio policy: fix global effect attachment

Fix logic for global music effects (e.g Visualizer) attachement to
output streams.
- Consider only outputs with active music sessions first and then all
outputs
- Reevaluate effect attachment systematically on music playback start/stop
and when outputs are opened/closed
- Use the same logic every where.

Bug: 33397379
Test: CTS: AudioEffectTest, VisualizerTest, EqualizerTest, BassBoostTest
      Manual test with music playback with and without Effects in
      offload and non offload mode on speaker, headset, BT A2DP.

Change-Id: Iabc23bc8a24f36b68942b7f32749c535781497b4