The macro list avoids duplication in external-reference-table and will
allow us to statically determine the size of the table in a follow-up.

TBR=mlippautz@chromium.org

Bug: v8:6666
Change-Id: I06bb2e8c25970b3c1047dafd6c63d7ca291fe37e
Reviewed-on: https://chromium-review.googlesource.com/956187
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51850}