refactor: Delete a lot of unused and duplicate code in Server and WebhookServer (#5080)

* store n8n version string in a const and use that everywhere

* reduce code duplication between Server and WebhookServer

* unify redis checks

* fix linting

packages/cli/src/UserManagement/Interfaces.ts

@@ -29,6 +29,5 @@ export interface N8nApp {
 	app: Application;
 	restEndpoint: string;
 	externalHooks: IExternalHooksClass;
-	defaultCredentialsName: string;
 	activeWorkflowRunner: ActiveWorkflowRunner;
 }