Making Rust observability reliable at scale with OpenTelemetry

To resolve fragmented and inconsistent observability in their Rust services, Datadog developed `dd-trace-rs`, an opinionated tracer built on OpenTelemetry that ensures consistent configuration and context propagation by default. Beyond creating this tool, the team contributed significant upstream fixes to the OpenTelemetry and `tracing` crates to improve interoperability and performance for the entire Rust ecosystem.