Add support for OpenTelemetry tracing (#1729)

* Also added TurnTrackingObserver, TurnTraceObserver, foundational 29, open-telemetry-example

examples/open-telemetry-tracing/env.example

@@ -0,0 +1,10 @@
+DEEPGRAM_API_KEY=your_deepgram_key
+CARTESIA_API_KEY=your_cartesia_key
+OPENAI_API_KEY=your_openai_key
+
+# Set to any value to enable tracing
+ENABLE_TRACING=true
+# OTLP endpoint (defaults to localhost:4317 if not set)
+OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317
+# Set to any value to enable console output for debugging
+# OTEL_CONSOLE_EXPORT=true