Consider moving to `oxnet` for basic address types

[bnaecker]

We should consider moving to oxnet for our core address types like IPs. We need some improvements to oxnet, like making it no_std before we do that, but it would help with a lot of confusion and conversions we're doing at the API boundary with Omicron.

[FelixMcFelix]

Agreed, at the very least for the ioctl/rules APIs. Today we have effectively two sets of network types in OPTE, too; those appearing in the ioctl/API side and those used in ingot for the actual dataplane work. I'm generally okay with maintaining an upper- and lower-level representation like that, since there are a lot more contracts needed to plug types into ingot and I think some of the crate relationships might get circuitous.

Saying that, there are some API-level types which are defined in Ingot which were taken from here (Vni etc.) for whom parsing from, e.g., text should probably be an oxnet thing.