By about 10x-20x depending on platform and configuration.
Shorter test strings make the set of all possible substrings
considerably smaller.

Fixed: v8:13074
Bug: v8:12868
Change-Id: I46ae94fbcba43080d06b1b825feae6b2acf819d1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3763861Reviewed-by: Andy Wingo <wingo@igalia.com>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81753}