Introduce device(s) role for strategy.

Adding interface for set/remove/getDevicesRoleForStrategy. This will be
used for setting device(s) role, such as preferred, for strategy.
Set/remove/getPreferreDeviceForStrategy are reimplemented by calling
the new interfaces.

Test: atest AudioHostTest
Test: atest AudioServiceHostTest
Test: atest AudioServiceTest
Test: atest audiopolicy_tests
Bug: 160352965
Change-Id: I2ba02c6b50af80846a25010ead05c4ae364868de