.. and replace them by elements read directly from the heap object.

With this change, consistency between `map` and `elements` is
no longer guaranteed. Users were updated, when necessary, to deal
with this, e.g. by being more careful not to read out of bounds,
by inserting new `actual_elements == elements_constant` runtime
checks, or through a new compilation dependency that verifies
unchanged elements at finalization time.

Drive-by: inline GetElementsKind into callsites.

Bug: v8:7790
Change-Id: Ifba78182e185ff0d4e954e3be52f0eb24328c853
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2909655Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74977}