Added runner for sharding egtests .

Runner runs test using command:

xcodebuild test-without-building -xctestrun file.xctestrun \
      -parallel-testing-enabled YES -parallel-testing-worker-count %d% \
      -destination "destination"  -resultBundlePath %output_path%

that allows to split tests between few clones of simulator
(`destination` parameter) and stores an entire output of the command
(session and diagnostic logs) in specified folder(`resultBundlePath`).

Change-Id: I0a50680bb6946d227ab19719c16cbecffc3f8456
Bug: 912323
Reviewed-on: https://chromium-review.googlesource.com/c/1330204
Commit-Queue: Maksym Onufriienko <monufriienko@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Sergey Berezin <sergeyberezin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616802}
5 files changed