Backend Plugins: Collect and expose metrics and plugin process health check (#21481)

Adds support for collecting metrics from backend plugins and 
exposing them thru Grafana's Prometheus metrics endpoint. 
Enables to check health of backend plugin by using the route
`/api/plugins/<plugin id>/health`.
Uses sdk v0.6.0.

Closes #20984

pkg/infra/metrics/metrics.go

@@ -148,6 +148,8 @@ var (
 
 	// grafanaBuildVersion is a metric with a constant '1' value labeled by version, revision, branch, and goversion from which Grafana was built
 	grafanaBuildVersion *prometheus.GaugeVec
+
+	grafanPluginBuildInfoDesc *prometheus.GaugeVec
 )
 
 func init() {
@@ -422,6 +424,12 @@ func init() {
 		Help:      "A metric with a constant '1' value labeled by version, revision, branch, and goversion from which Grafana was built",
 		Namespace: exporterName,
 	}, []string{"version", "revision", "branch", "goversion", "edition"})
+
+	grafanPluginBuildInfoDesc = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Name:      "plugin_build_info",
+		Help:      "A metric with a constant '1' value labeled by pluginId, pluginType and version from which Grafana plugin was built",
+		Namespace: exporterName,
+	}, []string{"plugin_id", "plugin_type", "version"})
 }
 
 // SetBuildInformation sets the build information for this binary
@@ -434,6 +442,10 @@ func SetBuildInformation(version, revision, branch string) {
 	grafanaBuildVersion.WithLabelValues(version, revision, branch, runtime.Version(), edition).Set(1)
 }
 
+func SetPluginBuildInformation(pluginID, pluginType, version string) {
+	grafanPluginBuildInfoDesc.WithLabelValues(pluginID, pluginType, version).Set(1)
+}
+
 func initMetricVars() {
 	prometheus.MustRegister(
 		MInstanceStart,
@@ -480,6 +492,7 @@ func initMetricVars() {
 		StatsTotalActiveEditors,
 		StatsTotalActiveAdmins,
 		grafanaBuildVersion,
+		grafanPluginBuildInfoDesc,
 	)
 
 }