This is a reland of 6798619a

Original change's description:
> [d8] Add d8 global variable
>
> - Add a a "d8" global variable where d8 can provide helpers.
>   This in in preparation of adding d8.log for testing our log parsers
>   written in JavaScript.
>
> - Separate d8 helper creation into individual functions.
>
> Bug: v8:1064
> Change-Id: I84e434452463afb93ae403f890d8841b20b00703
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2400990
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Commit-Queue: Camillo Bruni <cbruni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#69801}

TBR=verwaest@chromium.org

Bug: v8:1064
Change-Id: I656d550b5ec87dc52dbe6cbbdddf7151ce25031f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2403247
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69819}