This reverts commit 1025bf26.

Reason for revert: https://crbug.com/v8/12645

Original change's description:
> [shared-struct] Prototype JS shared structs
>
> Unlike the Stage 1 proposal, for simplicity the prototype does not add
> any new syntax, instead opting for exposing a SharedStructType
> constructor which takes an array of field names. This type constructor
> returns constructors for shared structs.
>
> Shared structs can be shared across Isolates, are fixed layout, have no
> prototype, have no .constructor, and can only store primitives and
> other shared structs.
>
> The initial prototype does not have TurboFan support.
>
> Bug: v8:12547
> Change-Id: I23bdd819940b42139692bcdb53d372099b0d4426
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3390643
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Reviewed-by: Marja Hölttä <marja@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Commit-Queue: Shu-yu Guo <syg@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#79156}

Bug: v8:12547
Change-Id: I44f2b8bb7487b4d39ba1282585e0b2282501230f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3474676
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79170}