fix(runtime-core): fix props/emits resolving with global mixins

fix #1975

packages/runtime-core/src/apiCreateApp.ts

@@ -33,6 +33,7 @@ export interface App<HostElement = any> {
   provide<T>(key: InjectionKey<T> | string, value: T): this
 
   // internal, but we need to expose these for the server-renderer and devtools
+  _uid: number
   _component: ConcreteComponent
   _props: Data | null
   _container: HostElement | null
@@ -108,6 +109,8 @@ export type CreateAppFunction<HostElement> = (
   rootProps?: Data | null
 ) => App<HostElement>
 
+let uid = 0
+
 export function createAppAPI<HostElement>(
   render: RootRenderFunction,
   hydrate?: RootHydrateFunction
@@ -124,6 +127,7 @@ export function createAppAPI<HostElement>(
     let isMounted = false
 
     const app: App = (context.app = {
+      _uid: uid++,
       _component: rootComponent as ConcreteComponent,
       _props: rootProps,
       _container: null,