In some objects, the length field for an indexed field might itself be
conditionally included depending on some previous field's value. The
module-related stuff at the end of ScopeInfo is a good example. Torque
can represent that case, with a minor change allowing indexed field
access from within the length expression for another indexed field.

Bug: v8:7793
Change-Id: I9ff5c9cea2b9423f28004beba05a9a24b22c8e3e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2360328Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#69457}