[EXPORTER] fix throw in OtlpGrpcMetricExporter with shared grpc client#3243

marcalff merged 2 commits intoopen-telemetry:mainopen-telemetry/opentelemetry-cpp:mainfrom

dbarker:fix_aggregation_temporality_throwdbarker/opentelemetry-cpp:fix_aggregation_temporality_throwCopy head branch name to clipboard