Bun Now Respects Container CPU Limits on Linux

Bun was previously ignoring Docker and Kubernetes CPU limits, spawning as many threads as the host had cores—causing severe performance issues and latency spikes in containerized deployments. This update makes Bun container-aware by routing CPU detection through Linux cgroup quotas, ensuring it correctly honors resource constraints like `docker run --cpus=2`. This fix is essential for production deployments and aligns Bun with Node.js behavior.