Previously, our Torque definition of JSArrayBuffer included only the
first two fields. This allowed access to those two fields, but was
somewhat confusing and obviously didn't let Torque code access the
other fields. This change:

- Completes the JSArrayBuffer layout definition;
- Moves the associated bitfield struct definition to Torque;
- Moves a couple of JSArrayBuffer macros to Torque;
- Adds a reducer case so that the code generated using these new macros
  is not worse than what was generated previously.

Change-Id: Ib19c3ba789a33801fa9d0d064cd21d62a1e03e30
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2053769
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66503}