[IMP] component: emit warning when async hooks take too long

This commit adds a warning when an async hook
(onWillUpdateProps/onWillStart) takes longer than 3 seconds, as these
hooks block the rendering and patching of the application, it is rarely
desirable and often a sign of a deadlock. This warning will contain the
stack trace of the call to the hook to help in debugging.

tests/helpers.ts

@@ -49,7 +49,7 @@ export async function nextTick(): Promise<void> {
 
 interface Deferred extends Promise<any> {
   resolve(val?: any): void;
-  reject(): void;
+  reject(val?: any): void;
 }
 
 export function makeDeferred(): Deferred {