chore: upgrade opentelemetry example to camel-opentelemetry2

Migrate the opentelemetry example from the deprecated
camel-opentelemetry to camel-opentelemetry2.

Changes:
- Replace camel-opentelemetry-starter with camel-opentelemetry2-starter
- Replace @CamelOpenTelemetry with @CamelOpenTelemetry2
- Fix Kafka broker URLs for host-to-Docker connectivity
- Remove stale/unused properties (opentracing, jaeger, etc.)

Note: the async (Kafka) trace context propagation is currently broken
in camel-opentelemetry2 due to a missing byte[] header handling in
camel-telemetry's AbstractMessagingSpanDecorator. A fix has been
proposed in Apache Camel.