Fix pose predictor jank.

There were two issues:
- A math error in angular velocity computation.
  This has unit tests and they were failing.
  Need to make sure these units tests get executed.

- There is an inherent sensor latency that we need to account for.

Bug: 36693596, 36196200
Test: Run VrHome, see less hanky result.
Change-Id: Ifcf191f16de9ee64aa14bcbb74c9126db18ebaa8