as part of the continuing quest to get rid of Object*/Object** entirely.
Since it fits nicely, this CL as a bonus includes the planned change to
make Handle::location() return an Address*, in the process dropping the
temporarily needed duplicate Handle::location_as_address_ptr().

Bug: v8:3770
Change-Id: I87480289ce2a62ea1ae503e73d179256b7108c5c
Reviewed-on: https://chromium-review.googlesource.com/c/1298389Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57153}