Add auth spans and remove deduplication code for scopes (#89804)

Adds more spans for timing in accesscontrol and remove permission deduplicating code after benchmarking

---------

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>
Co-authored-by: Dave Henderson <dave.henderson@grafana.com>
Co-authored-by: Ieva <ieva.vasiljeva@grafana.com>

pkg/services/authn/authnimpl/service.go

@@ -323,6 +323,9 @@ Default:
 }
 
 func (s *Service) ResolveIdentity(ctx context.Context, orgID int64, namespaceID authn.NamespaceID) (*authn.Identity, error) {
+	ctx, span := s.tracer.Start(ctx, "authn.ResolveIdentity")
+	defer span.End()
+
 	r := &authn.Request{}
 	r.OrgID = orgID
 	// hack to not update last seen
@@ -358,6 +361,9 @@ func (s *Service) IsClientEnabled(name string) bool {
 }
 
 func (s *Service) SyncIdentity(ctx context.Context, identity *authn.Identity) error {
+	ctx, span := s.tracer.Start(ctx, "authn.SyncIdentity")
+	defer span.End()
+
 	r := &authn.Request{OrgID: identity.OrgID}
 	// hack to not update last seen on external syncs
 	r.SetMeta(authn.MetaKeyIsLogin, "true")
@@ -365,6 +371,9 @@ func (s *Service) SyncIdentity(ctx context.Context, identity *authn.Identity) er
 }
 
 func (s *Service) resolveIdenity(ctx context.Context, orgID int64, namespaceID authn.NamespaceID) (*authn.Identity, error) {
+	ctx, span := s.tracer.Start(ctx, "authn.resolveIdentity")
+	defer span.End()
+
 	if namespaceID.IsNamespace(authn.NamespaceUser) {
 		return &authn.Identity{
 			OrgID: orgID,