chore: extract readiness in a dedicated utils crate (#4140)

Create an `utils` directory for the small utils crates

codex-rs/utils/readiness/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "codex-utils-readiness"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+async-trait = { workspace = true }
+thiserror = { workspace = true }
+time = { workspace = true }
+tokio = { workspace = true, features = ["sync", "time"] }
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["macros", "rt", "rt-multi-thread"] }
+
+[lints]
+workspace = true