Upgrade rmcp to 3.0.0 (#36001)

## What changed

- Update the Rust MCP SDK from `3.0.0-beta.3` to `3.0.0` and adapt to its renamed metadata and server discovery types.
- Accept discovery responses without server identity metadata, using the configured server name as a fallback, and rely on the SDK's native support for namespaced server identity metadata.
- Preserve typed OAuth HTTP errors so transport failures, cross-origin redirects, and transient HTTP responses are reported instead of being treated as anonymous access.

## Testing

- Cover modern discovery with namespaced or missing server identity over HTTP, SSE, and stdio.
- Cover OAuth discovery error propagation for transport failures, redirects, and transient status codes.

GitOrigin-RevId: 12c1e45136cca89ce4fb15986c2b5df14608682a

codex-rs/cli/tests/mcp_list.rs

@@ -165,6 +165,7 @@ async fn list_discovers_local_oauth_server_through_environment_proxy() -> Result
                     Err(error) => return Err(error.into()),
                 }
             };
+            stream.set_nonblocking(false)?;
             stream.set_read_timeout(Some(Duration::from_secs(5)))?;
             let mut request = Vec::new();
             let mut buffer = [0_u8; 1024];