We have 4 different cases:
1) Explicit web snapshots (--web-snapshot) & errors in the snapshot
2) Explicit web snapshots & errors in the embedded script
3) Auto-detected web snapshots (--experimental-web-snapshots) & errors
in the snapshot
4) Auto-detected web snapshots & errors in the embedded script

Before this CL: cases 2 & 4 resulted in a DCHECK failing and the error
in case 3 wasn't reported correctly.

This CL implements consistent error reporting for all of them.

Bug: v8:11525
Change-Id: If2e5039d9769b9cad2175dfd5c4f91edf61111ae
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3277877Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77963}