vm/mlvm/anonloader/stress/parallelLoad test uses a nested MlvmTest-derived test (vm.mlvm.anonloader.share.StressClassLoadingTest) inside other MlvmTest-derived test (vm.mlvm.share.MultiThreadedTest).

This is done in an incorrect way, so command-line options in the StressClassLoadingTest are ignored.

- MLVM tests should have some shared functionality to allow nested tests to have command-line options and other stuff as top-level ones.