This change does a few things involving the way we run the perf tests:

- Perf test runner can capture different metrics

Useful for capturing the new "nanoSecPerIteration" metric.

- Removes the "score" metric

We'll move to the new time-based metrics. These new metrics are scaled
correctly with iteration counts.

- Runs three trials per perf test

This gives more measurements per test. Each trial is approximately one
second. First the perf tests set a fixed number of iterations after
calibrating the number of steps that we can run in one second. After
that the three trials are run. This should give more stable results.

- Apply more CPU stabilization on Windows

Use SetPriorityClass to apply more CPU priority. Also upgrade
SetThreadPriority to the highest level.

- Always build the Vulkan command buffer test

This catches build regressions more easily. We still skip the test on
non-Android platforms.

Bug: angleproject:2923
Change-Id: I7da234c5af07775ba4a232bb8d65e0138ee7073f
Reviewed-on: https://chromium-review.googlesource.com/c/1330262
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>