This removes a shortcut to a "CEntryStub" from the instance object and
instead loads those values via the root set which is also referenced
from the instance. It makes instance objects smaller.

R=clemensh@chromium.org

Change-Id: I2e77cf2cb6949873bb461fb1ed0787e4a413aa5f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1714656
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62888}