This reverts commit 59eff3bf.

Reason for revert: Breaks UBSan - https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux64%20UBSan/16697/overview

Original change's description:
> [bigint] Karatsuba multiplication
>
> The Karatsuba algorithm is used for BigInts with 34 or more internal
> digits, and thanks to better asymptotic complexity provides greater
> speedups the bigger the inputs.
>
> Bug: v8:11515
> Change-Id: I5ab0e318173ea4a02ced3f156d3c17e0259c5036
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2782283
> Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74916}

Bug: v8:11515
Change-Id: Ifd3d651a26441ba36a23724c6eb1a9915f6e41a8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2933496
Auto-Submit: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#74918}