SurfaceFlinger: better fit content to refresh rate

Enhance the current algorithm for content based refresh rate selection
to choose a refresh rate that aligns better to the content. If no refresh
rate fits to the content we choose the lower one.

Fixes: 129874336
Test: Swappy render at 90fps, 45fps, 30fps
Test: Youtube video playback on 24fps, 25fps, 30fps, and 60fps
Change-Id: Ia6b1f2a1d78e257e0de99ba12c14ca3721b4ad26