Add support for stratis

[ermo]

Stratis is a Rust-developed LVM+xfs disk provisioning tool, which uses the stratis-daemon to call into the lower levels of the stack.

This issue is for tracking the compatibility story of disks-rs with stratis.

Chiefly, it might be cool if disks-rs could be made to recognise stratis-controlled pools, and potentially help provision storage for stratis to use?