Leverage illumos-rs

[rcgoodfellow]

The illumos-rs already has some general functionality that's implemented in OPTE.

For example

• oxidecomputer/illumos-rs#3

We should continue the trend of moving generally useful things to illumos-rs and then just import those things in OPTE and other rust-based drivers that need them. The rusty-modules branch also has a foundation for building drivers that would be great to leverage broadly. OPTE/XDE is the only rust module I'm aware of, but I'm starting to work on one for Redhawk.