- Add more conformance tests for proxy call and calling undetectable
- This improves the performance of calling a proxy by ~5x

Bug: v8:6558, v8:6557
Change-Id: I5fe78d7ca703cfe86a2a14e39f0b6d88bb8c8e03
Reviewed-on: https://chromium-review.googlesource.com/570023Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Maya Lekova <mslekova@google.com>
Cr-Commit-Position: refs/heads/master@{#46673}