Want versioned crate for Omicron networking types

[bnaecker]

In #10101 and #10070 (and others), we ran into issues trying to both version some networking types in omicron-common, and also pull those out of common entirely to slim things down. In #10101 at least, the issue was a circular dependency between those crates and illumos-utils. That latter is the point that we convert from Omicron types into OPTE types for firewall rules, and we can't easily pull out all the types because of the details of that conversion.

We probably want a new, versioned types crate for networking specifically. It might be hard to keep this from ballooning into a new omicron-common, but at least it will be versioned.