WIP: feat(zone): drop Command in favour of posix_spawn

This change introduces custom process spawning logic around
libc::posix_spawn/p, as well as a custom set of stdio wrappers using the
Tokio AsyncRead/AsyncWrite traits.

Currently this change is broken, stdio seeming to hang.

crates/zone/Cargo.toml

@@ -21,6 +21,7 @@ log = { workspace = true }
 nix = { workspace = true, features = ["ioctl", "process", "fs"] }
 oci-spec = { workspace = true }
 path-absolutize = { workspace = true }
+pin-project-lite = { workspace = true }
 platform-info = { workspace = true }
 rtnetlink = { workspace = true }
 serde = { workspace = true }