.. to consistently support more than a single argument.

Each argument is now a tagged union that may contain an AST string, a
C string, or a JS string handle.

Change-Id: Iac8e40b717dea95a2bc2903449dab56c181702d6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3122086
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76559}