Multitests with multiple VMOptions are not deflaked

[sortie]

When implementing support for tests with multiple VMOptions in the new workflow, requesting that test.py run such a test with a selector or --test-list wasn't implemented. That means tests such as standalone_2/io/dart_std_io_pipe_test/04/1 is not being deflaked properly and cause builds to fail due to flakes.

This should get fixed so tools/test.py --test-list standalone_2/io/dart_std_io_pipe_test/04/1 works properly. This would make the deflaking test.py run output results in results.json for such tests and deflaking would work properly.