SF: add anchor list to RefreshRateSelector

Use an anchor list instead of adding all divisors >= 20hz
when selecting the render rates SF can choose from, to allow
running or lower than 20hz rates.

Bug: 356986687
Test: presubmit + manual
Test: TouchLatency at 5fps
Flag: com.android.graphics.surfaceflinger.flags.anchor_list
Change-Id: Id9fa5bf057ce7160f6b1a8becdfafbf42bfb63c9