Add version to the internal telemetry metrics (#4140)

Added a version tag to the collector's own telemetry metrics because today when looking at those metrics there is no way to know the collector's version, this can also help to know what collector versions are running out there.
I based the "flag" to control this on [PR 3816](#3816)

Author: emaderer

service/telemetry.go

@@ -36,6 +36,7 @@ import (
 	"go.opentelemetry.io/collector/config/configtelemetry"
 	"go.opentelemetry.io/collector/internal/collector/telemetry"
 	"go.opentelemetry.io/collector/internal/obsreportconfig"
+	"go.opentelemetry.io/collector/internal/version"
 	semconv "go.opentelemetry.io/collector/model/semconv/v1.5.0"
 	"go.opentelemetry.io/collector/processor/batchprocessor"
 	telemetry2 "go.opentelemetry.io/collector/service/internal/telemetry"
@@ -44,6 +45,9 @@ import (
 // collectorTelemetry is collector's own telemetry.
 var collectorTelemetry collectorTelemetryExporter = &colTelemetry{}
 
+// AddCollectorVersionTag indicates if the collector version tag should be added to all telemetry metrics
+const AddCollectorVersionTag = true
+
 type collectorTelemetryExporter interface {
 	init(asyncErrorChannel chan<- error, ballastSizeBytes uint64, logger *zap.Logger) error
 	shutdown() error
@@ -79,6 +83,7 @@ func (tel *colTelemetry) initOnce(asyncErrorChannel chan<- error, ballastSizeByt
 	}
 
 	var instanceID string
+
 	if telemetry.GetAddInstanceID() {
 		instanceUUID, _ := uuid.NewRandom()
 		instanceID = instanceUUID.String()
@@ -104,6 +109,7 @@ func (tel *colTelemetry) initOnce(asyncErrorChannel chan<- error, ballastSizeByt
 		zap.String("address", metricsAddr),
 		zap.Int8("level", int8(level)), // TODO: make it human friendly
 		zap.String(semconv.AttributeServiceInstanceID, instanceID),
+		zap.String(semconv.AttributeServiceVersion, version.Version),
 	)
 
 	mux := http.NewServeMux()
@@ -148,10 +154,14 @@ func (tel *colTelemetry) initOpenCensus(level configtelemetry.Level, instanceID
 		Namespace: telemetry.GetMetricsPrefix(),
 	}
 
+	opts.ConstLabels = make(map[string]string)
+
 	if telemetry.GetAddInstanceID() {
-		opts.ConstLabels = map[string]string{
-			sanitizePrometheusKey(semconv.AttributeServiceInstanceID): instanceID,
-		}
+		opts.ConstLabels[sanitizePrometheusKey(semconv.AttributeServiceInstanceID)] = instanceID
+	}
+
+	if AddCollectorVersionTag {
+		opts.ConstLabels[sanitizePrometheusKey(semconv.AttributeServiceVersion)] = version.Version
 	}
 
 	pe, err := prometheus.NewExporter(opts)