otelgrpc: Remove the interceptors

[pellared]

I think we should also update the existing examples to use the new instrumentation.

I propose to:

1. Merge this PR
2. Create an issue for https://github.com/open-telemetry/opentelemetry-go-contrib/pull/3002/files#r1209293763
3. Update the existing examples to use the new functionality.
4. Deprecate the interceptors so that they are available in next release.
5. After the next release remove the interceptors.

@open-telemetry/go-approvers please upvote/downvote if you agree or not. Feel free to leave any additional feedback.

Originally posted by @pellared in #3002 (review)

Remove the interceptors after the deprecation is part of a release.

EDIT: We should still have the interceptors (even as deprecated) as long as https://pkg.go.dev/google.golang.org/grpc/stats is experimental API.

Blocked by:

• roadmap to make statsHandler stable grpc/grpc-go#4690