move Stabilizer to latest MQTT builds
I thought it would be a quick thing to end the week nicely but it will require moving from cargosha256 to Cargo.lock and updating Rust manifest to 2021+.
Thankfully we have no more Rust projects in non-flake, so it shouldn't be an issue.
However, what should we specify as the (new) MQTT broker IP address, since it's hardcoded during build? I doubt that we'd want to keep
Deleting a branch is permanent. It CANNOT be undone. Continue?