Wire with_remote_overrides to construct model families (#7621)

- This PR wires `with_remote_overrides` and make the
`construct_model_families` an async function
- Moves getting model family a level above to keep the function `sync`
- Updates the tests to local, offline, and `sync` helper for model
families

codex-rs/tui/Cargo.toml

@@ -105,6 +105,7 @@ arboard = { workspace = true }
 
 
 [dev-dependencies]
+codex-core = { workspace = true, features = ["test-support"] }
 assert_matches = { workspace = true }
 chrono = { workspace = true, features = ["serde"] }
 insta = { workspace = true }