netvsp: adding index oob tests for subchannel requests

[erfrimod]

Found crash dump from netvsp restore_queues()
driver: Box::new(drivers[queue_index as usize].clone()),

Should be fixed by #2430

• Adding unit test to validate.
• Copilot identified another possible way for the requested queues to exceed the drivers: during save/restore if the new NIC has fewer max_queues than previously. I don't think that is likely because we should be restoring on the exact same VM type. Added test that illustrates the issue and a trace statement that should help us diagnose it.