Making test262's GetExpectedOutcomes independent from a command.
It will enable us to move this function to precompute phase.

Bug: v8:6917
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: Ibb59da29bd30f32427ba6230a22d7d0801954bf0
Reviewed-on: https://chromium-review.googlesource.com/828933Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michał Majewski <majeski@google.com>
Cr-Commit-Position: refs/heads/master@{#50127}