OpenTelemetry tracing context in server/client context

[chazov-ts]

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

I'm implementing distributed tracing in a C++ application using gRPC and OpenTelemetry. My workflow involves creating spans within gRPC interceptors to trace request handling from start to finish. However, I'm encountering an issue where the tracing context created for a span in an interceptor is not readily accessible in subsequent handler functions. Currently, the only workaround is to manually pass this context via metadata and then reconstruct it in the handlers, which is inefficient and error-prone.
At the moment there is already a census_context field in contexts for similar ones for OpenCensus

Describe the solution you'd like

I propose a feature enhancement in the OpenTelemetry gRPC integration to allow direct storage and retrieval of the tracing context within the gRPC context. This would facilitate seamless access to the context in both server and client interceptors and throughout the request handling lifecycle without the need for manual metadata manipulation.

[yashykt]

This is gonna start seeing some updates soon. Please stay posted.