fix(types): make return type of defineComponent assignable to Component type (#1032)

fix #993

packages/runtime-core/__tests__/components/Suspense.spec.ts

@@ -11,7 +11,8 @@ import {
   watch,
   watchEffect,
   onUnmounted,
-  onErrorCaptured
+  onErrorCaptured,
+  Component
 } from '@vue/runtime-test'
 
 describe('Suspense', () => {
@@ -30,7 +31,7 @@ describe('Suspense', () => {
       setup(props: any, { slots }: any) {
         const p = new Promise(resolve => {
           setTimeout(() => {
-            resolve(() => h(comp, props, slots))
+            resolve(() => h<Component>(comp, props, slots))
           }, delay)
         })
         // in Node 12, due to timer/nextTick mechanism change, we have to wait