This reverts commit 6798619a.

Reason for revert: causing spurious optimisation failures.

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=cbruni@chromium.org,verwaest@chromium.org

Change-Id: I23b0c0a2ce28c13b3eba10a0eb15cd61967711d1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:1064
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2403246Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69804}