This generates and applies NetworkSettings object with unix socket IPC.
- domain socket, json-rpc based communication
- switches to anyhow for burrow crate
- adds support for starting daemons on macos
Those features are implemented using AsyncFD. While write doesn't
require a mutable reference to self, read does.
Make Async Tun a feature
remove async tun from workspace
rename write/read to send/recv
This involved refactoring the crate structure to share code between
macOS and Linux. The new methods have not yet been implemented on
macOS, but they have todo!() placeholders.