OpenTelemetry Stat Sink

The OpenTelemetryStatsSink configuration specifies a stat sink that emits stats according to OpenTelemetry Protocol Specification. The export requests of this sink are sent to the collector service according to the Protobuf defined in MetricService/Export. The metric resources exported are defined in metrics.proto. Any export request that this sink sends, will contain a single ResourceMetrics message, a single ScopeMetrics and repeated MetricRecord, according to the number of metrics collected during the proccess run.