This improves the num-fuzzer system test. Previously, the test
didn't actually start up the main functionality of num-fuzz and
executed 0 tests. Now several of the production fuzzers are used to
run fake test cases. The overall timeout signal, used to
stop numfuzz, is mocked with a counter. The observer signals via the
event method that would have caused the hang fixed in:
https://crrev.com/c/3891373

No-Try: true
Bug: v8:13113
Change-Id: I47d17c1fa2099474079acaad5640228d8c454eb1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3893807Reviewed-by: Alexander Schulze <alexschulze@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83243}