MetricReusableDataMarshaler passes MetricData count instead of data point count to otel.sdk.exporter.metric_data_point.{inflight,exported} #9011

Description

In MetricReusableDataMarshaler.export(Collection<MetricData> metrics), metrics.size() (the number of MetricData instruments) is passed as the item count to doExport:

In OtlpGrpcMetricExporter and OtlpHttpMetricExporter, doExport delegates to GrpcExporter.export(exportRequest, numItems) and HttpExporter.export(exportRequest, numItems), which pass numItems to ExporterInstrumentation.startRecordingExport(numItems) (SemConvExporterMetrics.startRecordingExport(numItems)), recording otel.sdk.exporter.metric_data_point.inflight and otel.sdk.exporter.metric_data_point.exported. When a MetricData contains multiple PointData entries (or 0 points), the recorded count reflects the number of metric instruments rather than the number of metric data points ({data_point}).

Expected behavior

otel.sdk.exporter.metric_data_point.inflight and otel.sdk.exporter.metric_data_point.exported should count the total number of metric data points (metricData.getData().getPoints().size()) across the exported Collection<MetricData>.