test_runner: use os.availableParallelism()
This commit addresses an existing TODO in the code by moving to the new os.availableParallelism() instead of os.cpus().length.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
This commit addresses an existing TODO in the code by moving to the new os.availableParallelism() instead of os.cpus().length.