Handlifies exception object as CollectSourcePositions can trigger GCs.

Bug: v8:8510
Change-Id: I29579b200af28bda30ccb5f2cf2e5a48f502c8f2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1664334
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62262}