Use pb.h for topology.proto.
Use pb.h for topology.proto.

This change uses pb.h instead of proto.h because OSS proto codegen doesn't support proto.h. The OSS conversion converts proto.h to pb.h in some directories but model_servers/ and examples/ are explicitly skipped.

PiperOrigin-RevId: 461780646

tensorflow/serving,tensorflow/serving,tensorflow/serving,tensorflow/serving