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/Cargo.lock

@@ -887,6 +887,7 @@ dependencies = [
  "codex-file-search",
  "codex-login",
  "codex-protocol",
+ "codex-rmcp-client",
  "codex-utils-json-to-toml",
  "core_test_support",
  "mcp-types",