The previous implementation would simply crash when command-line
parameters to the bigint_shell weren't valid integers (where
integers were expected).

Change-Id: Ia9987ab241ae9cac8dad4517766bfdd0b8cc98b7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3677295
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80824}