Add test for setOverrideFrameRate

- Create test to verify the API call in SurfaceComposerClient
- Create test to verify frame rate override DisplayEventReceiver events
are correctly received
- Add permission AID_ROOT to setOverrideFrameRate

Bug: b/204322816
Test: atest Surfaceflinger_test
Change-Id: I5b1782fcb7fc4896139ad56fcaee61853480f153