They've been replaced by JSFunctionBuilder.

Bug: v8:8888
Change-Id: Ie37e37befaf313fd58da3ecb02ab7c040e696f8e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2529134
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71102}