This reverts commit 3b065110.

Reason for revert: Broke fuzzers:
https://build.chromium.org/p/client.v8.clusterfuzz/builders/V8%20Deopt%20Fuzzer/builds/384

Original change's description:
> Reland "[test] Creating command before execution phase."
> 
> This is a reland of 98cc9e86
> Original change's description:
> > [test] Creating command before execution phase.
> > 
> > Immutable command class with shell, flags and
> > environment.
> > 
> > Command creation moved from worker to the main
> > process. Because of that there is no need to send
> > test cases beyond process boundaries and load test
> > suites in worker processes.
> > 
> > Bug: v8:6917
> > Change-Id: Ib6a44278095b4f7141eb9b96802fe3e8117678a6
> > Reviewed-on: https://chromium-review.googlesource.com/791710
> > Commit-Queue: Michał Majewski <majeski@google.com>
> > Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#49746}
> 
> Bug: v8:6917
> Change-Id: I49c29a8db813c47909f2cc45070ac7721a447c7a
> Reviewed-on: https://chromium-review.googlesource.com/800370
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Commit-Queue: Michał Majewski <majeski@google.com>
> Cr-Commit-Position: refs/heads/master@{#49756}

TBR=machenbach@chromium.org,sergiyb@chromium.org,majeski@google.com

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

Bug: v8:6917
Change-Id: I4938642c4396366be1e13daf6998c4b8538b688b
Reviewed-on: https://chromium-review.googlesource.com/804254Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49805}