Added synchronization of displays refresh rates

SurfaceFlinger supports only one refresh rate,
but in case displays have different refresh rates
this may lead to undesirable artifacts, also
during switching of internal display refresh rates
the external display may also blink for some reason.

This CL adds vote which aims to synchronize refresh
rates across displays.

Test: atest com.android.server.display.mode.DisplayObserverTest
Bug: 242093547
Change-Id: I0bf525c9b212a9b41efe43dcb32fbbe206892591