Navigation: Split admin into subsections behind navAdminSubsections feature toggle (#76280)

* split admin into subsections behind feature toggle

* make authentication a section header

* add translations for subsections

* rename translation keys

* add subtitles

pkg/api/index.go

@@ -166,7 +166,7 @@ func (hs *HTTPServer) setIndexViewData(c *contextmodel.ReqContext) (*dtos.IndexV
 
 	hs.HooksService.RunIndexDataHooks(&data, c)
 
-	data.NavTree.ApplyAdminIA()
+	data.NavTree.ApplyAdminIA(hs.Cfg.IsFeatureToggleEnabled(featuremgmt.FlagNavAdminSubsections))
 	data.NavTree.Sort()
 
 	return &data, nil