Panic with a clear message if the viona API is too old

[citrus-it]

Currently if one runs propolis on a system which does not have a new
enough viona API, a stacktrace like this is generated.

failed to enable promisc mode on vnic0: Os { code: 22, kind: InvalidInput, message: "Invalid argument" }
called `Result::unwrap()` on an `Err` value: Os { code: 25, kind: Uncategorized, message: "Inappropriate ioctl for device" }
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: propolis::hw::virtio::viona::PciVirtioViona::new_with_queue_sizes
   4: propolis::hw::virtio::viona::PciVirtioViona::new

Since we don't currently support anything older than the V6 API in
propolis we should at least produce a useful error message to the
operator. It would be possible to fall back to the older API if we
wish to implement that.

[dancrossnyc]

I think it may be a bit more idiomatic to use assert!() here. Something like:

Suggested change

	if virtio::viona::api_version().expect("can query viona version")
	let viona_version = virtio::viona::api_version().expect("got viona version");
	assert!(viona_version >= virtio::viona::ApiVersion::V6,
	"viona version {viona_version:?} is too old; need >= V6. Upgrade host OS");

[iximeow]

I could have sworn there was a place we check for version minimums here, but finding it took me a second: we probably should just bump compare in lib/propolis/src/hw/virtio/viona.rs to V6 and be done with it. both -standalone and -server end up calling that via api_version::check() to confirm some minimums. the check for viona V3 can go, too, now. I'll push a commit here in a bit.

[iximeow]

it ended up being a bit more distinct than I'd thought so #1027 takes a different swing at this. I included @dancrossnyc's suggestion that the OS is too old in the error there too.

[citrus-it]

Superseded by #1027