Google Cloud Propagator for OpenTelemetry

The `opentelemetry-propagator-gcp` library provides a TextMapPropagator for OpenTelemetry that handles the Google Cloud Trace context header (`x-cloud-trace-context`). It allows OpenTelemetry traces to be linked with existing traces in Google Cloud, facilitating interoperability. This library is part of the `opentelemetry-operations-python` project, is actively maintained, and follows a regular release cadence, typically monthly or bi-monthly, aligned with other OpenTelemetry SDK updates.