audioflinger: remove obsolete stream volume management

Remove the ability to change stream volume globally (on all outputs)
in audio flinger as this doesn't make sense when stream volume is
managed per device.

Also, do not store stream volumes globally in audio flinger and apply
them when a new output is opened. The ground truth for stream volume is
in audio policy so make sure stream volumes are systematically applied
by audio policy when an output is opened according to the selected device.

Bug: 70332110
Test: audio smoke tests
Change-Id: I7180a428af53aafdee82aadbcaf284c028ac5554