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/api/plugins.go

@@ -144,6 +144,7 @@ func (hs *HTTPServer) GetPluginList(c *contextmodel.ReqContext) response.Respons
 			AngularDetected: pluginDef.Angular.Detected,
 		}
 
+		//nolint:staticcheck // not yet migrated to OpenFeature
 		if hs.Cfg.ManagedServiceAccountsEnabled && hs.Features.IsEnabled(c.Req.Context(), featuremgmt.FlagExternalServiceAccounts) {
 			listItem.IAM = pluginDef.IAM
 		}
@@ -490,6 +491,7 @@ func (hs *HTTPServer) InstallPlugin(c *contextmodel.ReqContext) response.Respons
 		return response.ErrOrFallback(http.StatusInternalServerError, "Failed to install plugin", err)
 	}
 
+	//nolint:staticcheck // not yet migrated to OpenFeature
 	if hs.Cfg.ManagedServiceAccountsEnabled && hs.Features.IsEnabled(c.Req.Context(), featuremgmt.FlagExternalServiceAccounts) {
 		// This is a non-blocking function that verifies that the installer has
 		// the permissions that the plugin requests to have on Grafana.