When a call_indirect fails because of a signature mismatch or a null
target, the value stack generated for debug doesn't contain the target
index anymore, which makes it hard for users to understand the error.

Keep the index on the stack, and ensure that the index is not modified
until we generate the debug info. Previously, the index was shifted
in-place to compute various offsets. Instead, use scaled loads to
compute the offset directly in the load instruction.

R=clemensb@chromium.org

Bug: chromium:1350384
Change-Id: Iad5359ec80deef25a69ac119119a0b5ca559a336
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3854309Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82780}