Indead of just retrying the batch, retry individual tests.
This should correctly handle the Intel flake pattern.

Bug: angleproject:5415
Change-Id: I029c2514ff8e7a45184c5c105bf2d0350171da29
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2940049
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>