SurfaceFlinger: tune infrequent detection logic more

A layer will be considered frequent unless proven otherwise, in order
to make sure animations will change the refresh rate as soon as possible.
In addition, if a layer is classified infrequent, then we will keep it
infrequent until we get a burst of frames. These two policies combined
allow us to differentiate between an animating layer and a layer that
usually doesn't animate.

Bug: 157096772
Test: Play 24fps video in YouTube PIP mode and rotate the device - no jank
Test: Chrome playing video - no refresh rate switching
Test: Cursor blinking on Messages - switch to lowest refresh rate quickly
Change-Id: I3629b6e4786cd43919f51465e347f2abb52234d9