Code aging is no longer supported by any remaining compilers now
that full codegen has been removed. This CL removes all vestiges of
code aging.

BUG=v8:6409

Change-Id: I945ebcc20c7c55120550c8ee36188bfa042ea65e
Reviewed-on: https://chromium-review.googlesource.com/619153Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47501}