Add regression test for 8133023

The cause of the failure in 8133023 was the calculation of the ParallelGCThreads using information that had not yet been initialized. Add a test that checks that, after full initialization, the fresh calculation of ParallelGCThreads is consistent with the value calculated during VM initialization. This test does not check if the value of ParallelGCThreads is correctly calculated for the platform but only that the value calculated during VM initializationis consistent with a value calculated after VM initialization is complete.