Support Opentelemetry trace propagator for pubsub

[vigneshsn]

We have use case to pass the opentelemetry trace and span id's across the pubsub. it would be great, if we have this implemented as part quarkus extension rather than writing our own implementation. BTW we are using Quarkus extension for opentelemetry.

[jfbenckhuijsen]

@loicmathieu have also been looking at this for a bit last week, might be able to pick this up. Not sure on timeline, but seems doable.

[jfbenckhuijsen]

Upstream tracking issue for support in the Pubsub library itself: https://issuetracker.google.com/issues/183608476?pli=1

[jfbenckhuijsen]

Semantic conventions for Pubsub spec: https://opentelemetry.io/docs/specs/semconv/messaging/gcp-pubsub/

[jfbenckhuijsen]

Feature request in google-apis/java-pubsub googleapis/java-pubsub#1981