Add Monoio runtime support

Add support for the Monoio async runtime (thread-per-core, io_uring).

Description

Monoio is ByteDance's thread-per-core async runtime optimized for network applications.

Technical Context

• io_uring-based runtime
• Thread-per-core design
• Optimized for network I/O

Resources

• Monoio GitHub
• Monoio docs

Implementation Hints

• Look at existing runtime implementations in src/runtime/
• Create src/runtime/monoio.rs
• Add feature flag and optional dependency

Acceptance Criteria

• spawn_tracked function for Monoio
• InspectExt trait implementation
• Example in examples/ directory
• Feature flag: monoio-runtime