Access Control: Add histograms for evaluator and permissions checks (#34026)

This patch adds metrics to support instrumenting the accesscontrols package.
It also instruments the accesscontrol evaluator and the permissions function.

Co-authored-by: Vardan Torosyan <vardants@gmail.com>

pkg/services/accesscontrol/ossaccesscontrol/ossaccesscontrol.go

@@ -4,10 +4,12 @@ import (
 	"context"
 
 	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/grafana/grafana/pkg/infra/metrics"
 	"github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/services/accesscontrol"
 	"github.com/grafana/grafana/pkg/services/accesscontrol/evaluator"
 	"github.com/grafana/grafana/pkg/setting"
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 // OSSAccessControlService is the service implementing role based access control.
@@ -39,6 +41,9 @@ func (ac *OSSAccessControlService) Evaluate(ctx context.Context, user *models.Si
 
 // GetUserPermissions returns user permissions based on built-in roles
 func (ac *OSSAccessControlService) GetUserPermissions(ctx context.Context, user *models.SignedInUser) ([]*accesscontrol.Permission, error) {
+	timer := prometheus.NewTimer(metrics.MAccessPermissionsSummary)
+	defer timer.ObserveDuration()
+
 	builtinRoles := ac.GetUserBuiltInRoles(user)
 	permissions := make([]*accesscontrol.Permission, 0)
 	for _, builtin := range builtinRoles {