This reverts commit bee5992a.

Reason for revert: TSAN unhappiness https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux64%20TSAN/34656/overview

Original change's description:
> [wasm-gc] Initial Liftoff support
>
> This CL implements Liftoff support for struct.get/set,
> struct.new_with_rtt, rtt.canon, and ref.is_null, which
> is enough to make the first testcase pass.
>
> Bug: v8:7748
> Change-Id: Id09e9872d2126127192c852b3cb6d57ff9417582
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2584951
> Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71744}

TBR=jkummerow@chromium.org,clemensb@chromium.org

Change-Id: I1801c50861d74b7733ed828d6874f874fe8ba670
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7748
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2590674Reviewed-by: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71749}