- reduces default batch size from 1000 -> 256
- reduces default max processes to a max of 16
- stripes tests when in bot mode
- prints less spam when waiting for child processes

The striping and smaller batch size can help with slow tests.
The max process limit seemed to prevent errors on Linux.

Bug: angleproject:3162
Change-Id: Ibed89ca35db54c62ec8ed63b32bc5aed916faec9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2447037
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>