NGAlerting: Use identity.Requester interface instead of SignedInUser (#76360)

* unfurl SignedInUserAttrs services

* replace signedInUser with Requester

replace signedInUser with requester

* fix tests

* linting

---------

Co-authored-by: Ieva <ieva.vasiljeva@grafana.com>

pkg/services/navtree/navtreeimpl/admin.go

@@ -135,7 +135,7 @@ func (s *ServiceImpl) getAdminNode(c *contextmodel.ReqContext) (*navtree.NavLink
 	configNode := &navtree.NavLink{
 		Id:         navtree.NavIDCfg,
 		Text:       "Administration",
-		SubTitle:   "Organization: " + c.OrgName,
+		SubTitle:   "Organization: " + c.SignedInUser.GetOrgName(),
 		Icon:       "cog",
 		SortWeight: navtree.WeightConfig,
 		Children:   configNodes,