feat: support mcp in-session login (#7751)

### Summary
* Added `mcpServer/oauthLogin` in app server for supporting in session
MCP server login
* Added `McpServerOauthLoginParams` and `McpServerOauthLoginResponse` to
support above method with response returning the auth URL for consumer
to open browser or display accordingly.
* Added `McpServerOauthLoginCompletedNotification` which the app server
would emit on MCP server login success or failure (i.e. timeout).
* Refactored rmcp-client oath_login to have the ability on starting a
auth server which the codex_message_processor uses for in-session auth.

codex-rs/app-server/src/message_processor.rs

@@ -59,6 +59,7 @@ impl MessageProcessor {
             outgoing.clone(),
             codex_linux_sandbox_exe,
             Arc::clone(&config),
+            cli_overrides.clone(),
             feedback,
         );
         let config_api = ConfigApi::new(config.codex_home.clone(), cli_overrides);