refactor(types): widen Component type to include consutructor types

returned from `defineComponent`

ref: https://github.com/vuejs/vue-router-next/pull/421
also close #1880

Previous `Component` type is now exported as `ConcreteComponent`.

This introduces a minor breaking change when calling `h(comp, { ... })`
will now fail if `comp` is a of generic `Component` type, since it does
not specify what props it expects.

packages/runtime-core/src/helpers/resolveAssets.ts

@@ -1,7 +1,7 @@
 import { currentRenderingInstance } from '../componentRenderUtils'
 import {
   currentInstance,
-  Component,
+  ConcreteComponent,
   FunctionalComponent,
   ComponentOptions
 } from '../component'
@@ -16,7 +16,9 @@ const DIRECTIVES = 'directives'
 /**
  * @private
  */
-export function resolveComponent(name: string): Component | string | undefined {
+export function resolveComponent(
+  name: string
+): ConcreteComponent | string | undefined {
   return resolveAsset(COMPONENTS, name) || name
 }
 
@@ -49,7 +51,7 @@ function resolveAsset(
   type: typeof COMPONENTS,
   name: string,
   warnMissing?: boolean
-): Component | undefined
+): ConcreteComponent | undefined
 // overload 2: directives
 function resolveAsset(
   type: typeof DIRECTIVES,