This reverts commit bf78435b.

Reason for revert: This CL is not what I wanted to land. I mixed up my local branches.

Original change's description:
> [wasm] Stage wasm-bigint
> 
> The implementation on wasm-bigint has been done, as far as I can tell.
> There are no spec tests yet, only an out-dated copy of the original
> spec tests which don't pass anymore. Therefore I disabled all the tests
> for now and created a tracking bug at https://crbug.com/v8/9673.
> 
> R=​adamk@chromium.org
> 
> Bug: v8:7741, v8:9673
> Change-Id: I015846cc6008ad266402b6835e634723a1a076da
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1781050
> Commit-Queue: Andreas Haas <ahaas@chromium.org>
> Reviewed-by: Adam Klein <adamk@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#63541}

TBR=adamk@chromium.org,ahaas@chromium.org

Change-Id: I5e8a42ad01200c01446efe4ea50f8ae6fef2c174
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7741, v8:9673
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1784279Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63546}