chore : Deprecating FeatureToggles.IsEnabled (#113062)

* Deprecating features.IsEnabled

* add one more nolint

* add one more nolint

* Give better hints to devs in the deprecation message of IsEnabledGlobally

* adding more doc strings

* fix linter after rebase

* Extend deprecation message

pkg/services/ngalert/api/api_testing.go

@@ -79,6 +79,7 @@ func (srv TestingApiSrv) RouteTestGrafanaRuleConfig(c *contextmodel.ReqContext,
 		return response.ErrOrFallback(http.StatusInternalServerError, "failed to authorize access to rule group", err)
 	}
 
+	//nolint:staticcheck // not yet migrated to OpenFeature
 	if srv.featureManager.IsEnabled(c.Req.Context(), featuremgmt.FlagAlertingQueryOptimization) {
 		if _, err := store.OptimizeAlertQueries(rule.Data); err != nil {
 			return ErrResp(http.StatusInternalServerError, err, "Failed to optimize query")
@@ -178,6 +179,7 @@ func (srv TestingApiSrv) RouteEvalQueries(c *contextmodel.ReqContext, cmd apimod
 	}
 
 	var optimizations []store.Optimization
+	//nolint:staticcheck // not yet migrated to OpenFeature
 	if srv.featureManager.IsEnabled(c.Req.Context(), featuremgmt.FlagAlertingQueryOptimization) {
 		var err error
 		optimizations, err = store.OptimizeAlertQueries(cond.Data)
@@ -223,6 +225,7 @@ func addOptimizedQueryWarnings(evalResults *backend.QueryDataResponse, optimizat
 }
 
 func (srv TestingApiSrv) BacktestAlertRule(c *contextmodel.ReqContext, cmd apimodels.BacktestConfig) response.Response {
+	//nolint:staticcheck // not yet migrated to OpenFeature
 	if !srv.featureManager.IsEnabled(c.Req.Context(), featuremgmt.FlagAlertingBacktesting) {
 		return ErrResp(http.StatusNotFound, nil, "Backgtesting API is not enabled")
 	}