petri: storage: support hyper-v nvme dda

[mattkur]

(see comments in code)

When adding support for NVMe storage on Hyper-V VMs, I took the most expedient path and just did it using NVMe backed by VHDs. Generalize that support to also leverage DDA if configured.

Would need:

• Global device allocator (and test fallback behavior if there aren't other devices, if another test trial is using all of them, etc.). Be sure to handle any sort of resource leaks from test failures.
• Changes to petri and hyperv.psm1 to leverage said allocator.

[mattkur]

As of October 11, 2025, also tracked by Microsoft-internal issue number 59747643