[instrumentation-grpc] emit metrics according to semantic conventions

[pichlermarc]

Description

Note

This issue is in refinement stage, requirements and blockers are subject to change

Warning

The three issues linked below (#4897, semconv updates) are REQUIRED to be finished before implementation of this feature can start. Any PR opened to add this hook before these are finished will be rejected.

Once Semantic Conventions for @opentelemetry/instrumentation-grpc have been updated to latest, we can implement gRPC metrics according to the Semantic Conventions

The following items need to be done before implemented

• Implement stable http semantic conventions #4897
• RPC Metrics Semantic Conventions MUST be stable
• gRPC Metrics Semantic Conventions MUST be stable

This issue is considered done when

• RPC Metrics Semantic Conventions are implemented in @opentelemetry/instrumentation-grpc
• gRPC Metrics Semantic Conventions are implemented in @opentelemetry/instrumentation-grpc
• README.md and docs are updated to reflect the new state