The tests are generated randomly, using Python's arbitrary-precision
integers as the source of truth.
The generator script is landed as part of this CL. It also supports
a "stress test" mode for on-demand intensive test coverage.

Bug: v8:6791
Change-Id: Idc7a2e90fd8a0a8176283614b33ecd4c3597b1d1
Reviewed-on: https://chromium-review.googlesource.com/731464
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48844}