All stubs have been migrated to builtins. This CL removes most related
code.

Bug: v8:7777, v8:5784
Change-Id: I4470cfef34788e6c8e0fd5fd09e40e250d088dad
Reviewed-on: https://chromium-review.googlesource.com/c/1365284
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58093}