SF: Remove display lookup in SurfaceTracing

Remove the strong reference to prevent a removed display from being
destroyed off the main thread. This is also a step in adding thread
annotations to display state accessors.

Also, clean up SurfaceTracing usage in the SurfaceFlinger class.

Bug: 123715322
Test: Tracing still works.
Change-Id: Iad174e7b42fbde96a46155c740838f6cd3966365