Added MCP server command to enable authentication using ChatGPT (#2373)

This PR adds two new APIs for the MCP server: 1) loginChatGpt, and 2)
cancelLoginChatGpt. The first starts a login server and returns a local
URL that allows for browser-based authentication, and the second
provides a way to cancel the login attempt. If the login attempt
succeeds, a notification (in the form of an event) is sent to a
subscriber.

I also added a timeout mechanism for the existing login server. The
loginChatGpt code path uses a 10-minute timeout by default, so if the
user fails to complete the login flow in that timeframe, the login
server automatically shuts down. I tested the timeout code by manually
setting the timeout to a much lower number and confirming that it works
as expected when used e2e.

codex-rs/login/tests/login_server_e2e.rs

@@ -100,6 +100,7 @@ fn end_to_end_login_flow_persists_auth_json() {
         port: 0,
         open_browser: false,
         force_state: Some(state),
+        login_timeout: None,
     };
     let server = run_login_server(opts, None).unwrap();
     let login_port = server.actual_port;
@@ -158,6 +159,7 @@ fn creates_missing_codex_home_dir() {
         port: 0,
         open_browser: false,
         force_state: Some(state),
+        login_timeout: None,
     };
     let server = run_login_server(opts, None).unwrap();
     let login_port = server.actual_port;