When there are multiple nested catch blocks, the rethrow immediate
disambiguates which catch block to take the exception from. We
add a FixedArray to keep track of exceptions that are currently
in scope, and compute the mappings between rethrow/catch instructions
and the index to fetch/store the exception from/to in the FixedArray
during pre-processing.

R=clemensb@chromium.org

Bug: v8:8091
Change-Id: If55242c551f42262c790b5bf3f1543a003280623
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2695388
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72768}