support for MacOS Hypervisor.framework with multiple sandboxes #1796

#1674 added single sandbox suppot on macos. We should be able to support multiple sandboxes in parallel but there are some Hypervisor.framework api's that are missing/buggy. This is a place holder for that when it becomes ready.

There is also an approach for creating multiple sandboxes via remote processes that would do a similar thing but might have a higher overhead and that approach is covered in #1706. Both can be supported simultaneously.