This reverts commit 573d7f34.

Reason for revert: Breaking ANGLE roll.

No-try: true

Original change's description:
> Test Runner: Pick single/multi-process mode automatically.
>
> This enables multi-process when running with more than one test
> config. This saves developers from remembering to add the arg.
> It can also simplify our test configurations by allowing us to omit
> the default arguments. On Android by default we stay with single
> process. It also changes the --bot-mode flag into --single-process
> and --multi-process which override the default behaviour.
>
> Bug: angleproject:5585
> Change-Id: I3dd885a8a8e6604c224693c546ff5d15224e016e
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2664246
> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
> Reviewed-by: Kenneth Russell <kbr@chromium.org>
> Commit-Queue: Jamie Madill <jmadill@chromium.org>

TBR=kbr@chromium.org,syoussefi@chromium.org,jonahr@google.com,jmadill@chromium.org,jonahr@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: angleproject:5585
Change-Id: I11ee1034c301aa246c4b03e29ff9b56235a1005c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2676247Reviewed-by: Jamie Madill <jmadill@chromium.org>