This shares logic for finding additional resources in JS source code.
Previously the logic was implemented for mjsunit, now it will be used
across all d8-based test cases.

This'll enable adding those test suites for Android testing.

Bug: chromium:866862
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I7c89ba141483aaf692a03c0e168edb61bbb7b010
Reviewed-on: https://chromium-review.googlesource.com/1193873
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55503}