* fix: resolve gRPC DNS resolution issues in Kubernetes #8384
- Replace direct `grpc.NewClient` calls with `pb.GrpcDial` for consistent connection establishment
- Fix async DNS resolution behavior in K8s with `ndots:5`
- Ensure high-level components use established helper for reliable networking
* refactor: refine gRPC DNS fix and add documentation
- Use instance's grpcDialOption in BrokerClient.ConfigureTopic
- Add detailed comments to GrpcDial explaining Kubernetes DNS resolution rationale
* fix: ensure proper context propagation in broker_client gRPC calls
- Pass the provided `ctx` to `pb.GrpcDial` in `ConfigureTopic` and `GetUnflushedMessages`
- Ensures that timeouts and cancellations are correctly honored during connection establishment
* docs: refine gRPC resolver documentation and cleanup dead code
- Enhanced documentation for `GrpcDial` with explicit warnings about global state mutation when using `resolver.SetDefaultScheme("passthrough")`.
- Recommended `passthrough:///` prefix as the primary migration path for `grpc.NewClient`.
- Removed dead commented-out code for `grpc.WithBlock()` and `grpc.WithTimeout()`.
Chris Lu