Revert of [swarming] Isolate v8 testing. (patchset #8 id:140001 of https://codereview.chromium.org/1380593002/ )

Reason for revert:
Prime suspect in breakage of V8 Linux -- no snap

Original issue's description:
> [swarming] Isolate v8 testing.
>
> Add gyp support and isolates for default test suites.
> Add two default isolates, one (default) for using the
> test suite collection we call "default" on the bots. One
> (developer_default) for also supporting the way developers
> call the driver (i.e. without argument, which includes
> the unittests).
>
> BUG=chromium:535160
> LOG=n
>
> Committed: https://crrev.com/9bd83f58f29ab0c7c5b71b00bcb1df3a9e641f05
> Cr-Commit-Position: refs/heads/master@{#31081}

TBR=tandrii@chromium.org,jochen@chromium.org,maruel@chromium.org,machenbach@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:535160

Review URL: https://codereview.chromium.org/1370993008

Cr-Commit-Position: refs/heads/master@{#31084}