experimental/stats: re-add type aliases for migration (#7929)

experimental/stats/metrics.go

@@ -19,6 +19,8 @@
 // Package stats contains experimental metrics/stats API's.
 package stats
 
+import "google.golang.org/grpc/stats"
+
 // MetricsRecorder records on metrics derived from metric registry.
 type MetricsRecorder interface {
 	// RecordInt64Count records the measurement alongside labels on the int
@@ -37,3 +39,16 @@ type MetricsRecorder interface {
 	// gauge associated with the provided handle.
 	RecordInt64Gauge(handle *Int64GaugeHandle, incr int64, labels ...string)
 }
+
+// Metrics is an experimental legacy alias of the now-stable stats.MetricSet.
+// Metrics will be deleted in a future release.
+type Metrics = stats.MetricSet
+
+// Metric was replaced by direct usage of strings.
+type Metric = string
+
+// NewMetrics is an experimental legacy alias of the now-stable
+// stats.NewMetricSet.  NewMetrics will be deleted in a future release.
+func NewMetrics(metrics ...Metric) *Metrics {
+	return stats.NewMetricSet(metrics...)
+}