Add in-process app server and wire up exec to use it (#14005)

This is a subset of PR #13636. See that PR for a full overview of the
architectural change.

This PR implements the in-process app server and modifies the
non-interactive "exec" entry point to use the app server.

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Co-authored-by: Felipe Coury <felipe.coury@gmail.com>

codex-rs/exec/Cargo.toml

@@ -19,8 +19,11 @@ workspace = true
 anyhow = { workspace = true }
 clap = { workspace = true, features = ["derive"] }
 codex-arg0 = { workspace = true }
+codex-app-server-client = { workspace = true }
+codex-app-server-protocol = { workspace = true }
 codex-cloud-requirements = { workspace = true }
 codex-core = { workspace = true }
+codex-feedback = { workspace = true }
 codex-otel = { workspace = true }
 codex-protocol = { workspace = true }
 codex-utils-absolute-path = { workspace = true }