RBAC: Allow scoping access to root level dashboards (#76987)

* correctly check permissions to list dashboards on the root

* correctly display the access inherited from general folder for dashboards

* Update pkg/services/sqlstore/permissions/dashboard.go

Co-authored-by: Gabriel MABILLE <gamab@users.noreply.github.com>

* Update dashboard_filter_no_subquery.go

---------

Co-authored-by: Gabriel MABILLE <gamab@users.noreply.github.com>

pkg/services/accesscontrol/ossaccesscontrol/permissions_services.go

@@ -163,7 +163,7 @@ func ProvideDashboardPermissions(
 				}
 				return append([]string{parentScope}, nestedScopes...), nil
 			}
-			return []string{}, nil
+			return []string{dashboards.ScopeFoldersProvider.GetResourceScopeUID(folder.GeneralFolderUID)}, nil
 		},
 		Assignments: resourcepermissions.Assignments{
 			Users:           true,