Names of external references are statically known, so there is no need
to store them in the dynamically generated ExternalReferenceTable.
This saves 7.4kB per Isolate, plus ~46.4kB binary size.

R=mstarzinger@chromium.org

Bug: v8:8562
Change-Id: Ia494de38474e0a7308563ab6d1797ff488b0a072
Reviewed-on: https://chromium-review.googlesource.com/c/1369947Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58128}