Add more logs to debug nvme servicing CI failures

[mattkur]

• user_driver: backoff 250ms in set_keep_alive, just like open_device
• copilot pr feedback
• nvme_manager: re-enable multi-device servicing test, add some more logs to try and track down the problem
• more logs

[github-actions]

⚠️ Unsafe Code Detected

This PR modifies files containing unsafe Rust code. Extra scrutiny is required during review.

For more on why we check whole files, instead of just diffs, check out the Rustonomicon

[Copilot]

Pull request overview

This is a debugging PR (marked "DO NOT MERGE") aimed at investigating NVMe servicing CI test failures. The changes add comprehensive logging and implement async retry logic to handle race conditions in VFIO device initialization.

Key Changes:

• Converted VFIO open_device and set_keep_alive functions from synchronous to async to enable proper async delays instead of blocking thread sleeps
• Added retry logic with 250ms backoff to set_keep_alive to handle ENODEV race conditions, matching existing behavior in open_device
• Re-enabled the many_nvme_devices_servicing_heavy test that was previously ignored due to reliability issues
• Added debug/info logging at critical points in NVMe manager initialization and worker lifecycle

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
vmm_tests/vmm_tests/tests/tests/x86_64/openhcl_linux_direct.rs	Re-enables previously ignored multi-device NVMe servicing test
vm/devices/user_driver/vfio_sys/src/lib.rs	Converts open_device and set_keep_alive to async with retry logic for ENODEV handling; improves logging with PCI ID context
vm/devices/user_driver/vfio_sys/Cargo.toml	Adds pal_async dependency required for async timer functionality
vm/devices/user_driver/src/vfio.rs	Updates callers to use async open_device and set_keep_alive functions
openhcl/underhill_core/src/worker.rs	Adds debug logging after NVMe manager initialization
openhcl/underhill_core/src/nvme_manager/manager.rs	Adds info logging for manager startup parameters and debug logging before main loop
Cargo.lock	Reflects new pal_async dependency in vfio_sys package

[github-actions]

At least one Petri test failed.