SF: Adding callback to Scheduler for setting refresh rate to 60 and 90.

When device is idle, refresh rate is set to 60. When not it's set to 90.

See go/surface-flinger-scheduler for more info.

Test: All SF tests pass.
Bug: 113612090
Bug: 122347908
Change-Id: Ica6e483118db276f72d3cb4e79535303c76f99d7