Deal with unreliable VSYNC signals due to scheduler.

We see two sources of scheduler jank when waiting for VSYNC:
  - A kernfs issue that wakes up threads using a normal priority
    work queue that may be delayed or have other work on it.
  - The VSYNC callback from HWC is handled by a normal priority
    HwBinder thread that may be delayed by other work.

Change the VrFlinger frame post thread to use an absolute timer-
based dead reckoning loop. VSYNC timestamps from the display
driver are reliable, even if the delivery of the value takes time.
Predict the VSYNC time into the future based on the last known
VSYNC time. If we see that VSYNC has not been signaled by the time
we need to post a frame to HWC we assume that the driver and/or
HWC was delayed so much that the previous frame is still pending
and skip the upcoming frame to avoid double stuffing the driver.

Bug: 65064949
Test: Extensive system tests and systraces. See bug for details.
Change-Id: Iae6c4173b8eac1d179adc3fc8004d3d475b3f156