This CL adds the globals index space to the JS debug proxy as well as the
stack object. It also adds few small helpers to simplify the proxy setup
a little, since all index spaces work exaclty the same.

Bug: chromium:1127914
Change-Id: I707292ab7f44aafb73751c17fdacfef976316f39
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2448468
Commit-Queue: Philip Pfaffe <pfaffe@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70332}