Missing arguments are identical to undefined, and are converted to the
integer 0 by ECMAScript {ToInteger()}.
Add more tests, and enable previously disabled tests.

There is a follow-up refactoring here: https://crrev.com/c/704586

R=titzer@chromium.org, mstarzinger@chromium.org

Change-Id: I89cc259aaf5975ec2f6f51ff002e7d1b32adba5e
Reviewed-on: https://chromium-review.googlesource.com/704658Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48373}