(mostly for roots, handles and stack locations).
Thi CL also changes RootVisitor interface to use FullObjectSlots instead of
ObjectSlots.

Bug: v8:8518
Change-Id: I217c7ae176387a8c64f4754e62339727bdb36018
Reviewed-on: https://chromium-review.googlesource.com/c/1366035Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58091}