As the TODO's indicate, these helpers only used by TypedArray#join when it was
implemented in JS.  As of https://chromium-review.googlesource.com/c/v8/v8/+/1369330
TypedArray#join is now implemented Torque and was optimized in a way that no longer
requires these helpers anymore.

Bug: v8:7624
Change-Id: I1d1ff80235a12feb3846ff92764e8593ce7c72c9
Reviewed-on: https://chromium-review.googlesource.com/c/1498692Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Peter Wong <peter.wm.wong@gmail.com>
Cr-Commit-Position: refs/heads/master@{#59999}