Introduce device(s) role for strategy.

Adding interface to get/set/removeDevicesRoleForStrategy. The interfaces
allows to modify the devices' role, such as preferred, for strategy.
Get/set/removePreferredDeviceForStrategy is reimplemented by the new
interfaces.

Test: atest AudioHostTest
Test: atest AudioServiceHostTest
Test: atest AudioServiceTest
Test: atest audiopolicy_tests
Bug: 160352965
Change-Id: I0af737542a8599938cae4e142b733159f21ed5a8
Merged-In: I0af737542a8599938cae4e142b733159f21ed5a8