Decouple trace context propagation functionality for gRPC into a separate library

[nareshz]

Is your feature request related to a problem? Please describe.

We want to propagate trace context using W3 Trace Context header(traceparent) in gRPC requests made by using Spanner client library.

Currently https://github.com/open-telemetry/opentelemetry-java-instrumentation/tree/main/instrumentation/grpc-1.6/library provides GrpcTelemetry ClientInterceptor which can be used to intercept gRPC calls and add trace context headers in calls. The issue is that this library is in alpha version due to work going on semantic conventions.

We want to avoid adding alpha version library inside Spanner client library for trace context propagation as it may have breaking change in the future and instead use a stable one.

Describe the solution you'd like

Creating a stable library specific to only trace context propagation can solve the issue.

Describe alternatives you've considered

No response

Additional context

No response

[breedx-splk]

I'm not aware of any precedent for this -- factoring out the context extraction and propagation into its own module. Even if we were to do this, I'm not entirely convinced that it would "stabilize" (go non-alpha) somehow faster than the library instrumentation would. I appreciate that you're wanting to be able to use parts of the instrumentation in the spanner client, though.