Add sample "Observability with Spring Boot 3"

[MikeR13]

Hi there
We are migrating to Spring Boot 3.x. We have Spring Cloud Stream in use, specifically the SCS Binder from Solace. We have done experiments with micrometer-tracing-bridge-otel and micrometer-tracing-bridge-brave. The tracing information is not propagated with either of them, so no headers are set in the messages.
It would be nice to have an example of how this works new, with Spring Boot 3.x.