Hide accurate onFrameRendered calls behind render metrics feature flag

onFrameRendered calls were modified to be based on present fences,
instead of firing immediately after the app releases the buffer to
SurfaceFlinger. Hide this modification behind the render metrics feature
flag to avoid problems encountered by dogfooders.

Bug: 294920725
Test: add log statements to verify legacy mechanism for onFrameRendered
calls is switchable with the video render metrics feature flag

Change-Id: Ia6f74d8ab72a20eaf167273a1944eddb56f87284