APM: make AudioPolicyMixCollection inherit from Vector

  Modify AudioPolicyMixCollection to inherit from Vector instead
of KeyedVector so all so the collection of mixes stays in the same
order as the mixes were added.
  Also make the mix selection take the deviceType into consideration,
not just the address to enable the same address to be associated to
different devices.

Bug: 131090322
Test: see bug for multi bus scenario
Test: atest AudioPlaybackCaptureTest

Change-Id: I4dc7f23bef19a7d47afc2998102da07dde41fbca