[v7.5.x]: FrontendMetrics: Adds new backend api that frontend can use to push frontend measurements and counters to prometheus (#33255)

* Backport of https://github.com/grafana/grafana/pull/32593

* Update prometheus.yml

pkg/api/api.go

@@ -10,6 +10,7 @@ import (
 	"github.com/grafana/grafana/pkg/api/frontendlogging"
 	"github.com/grafana/grafana/pkg/api/routing"
 	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/grafana/grafana/pkg/infra/metrics"
 	"github.com/grafana/grafana/pkg/middleware"
 	"github.com/grafana/grafana/pkg/models"
 )
@@ -397,6 +398,8 @@ func (hs *HTTPServer) registerRoutes() {
 			annotationsRoute.Post("/graphite", reqEditorRole, bind(dtos.PostGraphiteAnnotationsCmd{}), routing.Wrap(PostGraphiteAnnotation))
 		})
 
+		apiRoute.Post("/frontend-metrics", bind(metrics.PostFrontendMetricsCommand{}), routing.Wrap(hs.PostFrontendMetrics))
+
 		// short urls
 		apiRoute.Post("/short-urls", bind(dtos.CreateShortURLCmd{}), routing.Wrap(hs.createShortURL))
 	}, reqSignedIn)