OpenTelemetry: DataDog all-in-one example

[grouzen]

Currently we provide an example of Jaeger tracer usage in opentelemetry-example. There is a demand to add the example of DataDog tracer usage too. It would be good to make both opentelemetry-example and opentelemetry-instrumentation-example work with DataDog.

Related: #686

[grouzen]

Discord thread that could be helpful: https://discord.com/channels/629491597070827530/639825316021272602/1161591495598551061

[grouzen]

Need to research the Free plan provided by DD: https://www.datadoghq.com/pricing/

[grouzen]

Now the zio-opentelemetry module supports all types of OTEL signals and it is time to add a full example for DD since it is one of the most-known platforms that allows showing metrics, traces, and logs in one place.

[jivanic-demystdata]

FYI, I just made a new micro-lib to help you configure zio-opentelemetry to work with the Datadog APM: https://x.com/guizmaii/status/1806702414063612123