fix(ts): use AppProps's generic for pageProps (#38867)

Currently, you cannot set `pageProps`'s type when using `AppProps`'s generic, it's always `any`.

Before:
![image](https://user-images.githubusercontent.com/18369201/180234440-3b37460c-ff92-413f-9d1c-38e35e35a5b4.png)


After:
![image](https://user-images.githubusercontent.com/18369201/180234644-335eec85-0315-4ff8-aba1-53edf0b64e1a.png)



## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm lint`
- [ ] The examples guidelines are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing.md#adding-examples)

packages/next/shared/lib/utils.ts

@@ -165,15 +165,15 @@ export type AppContextType<R extends NextRouter = NextRouter> = {
   router: R
 }
 
-export type AppInitialProps = {
-  pageProps: any
+export type AppInitialProps<P = any> = {
+  pageProps: P
 }
 
 export type AppPropsType<
   R extends NextRouter = NextRouter,
   P = {}
-> = AppInitialProps & {
-  Component: NextComponentType<NextPageContext, any, P>
+> = AppInitialProps<P> & {
+  Component: NextComponentType<NextPageContext, any, any>
   router: R
   __N_SSG?: boolean
   __N_SSP?: boolean

test/integration/app-tree/pages/_app.tsx

@@ -7,7 +7,7 @@ import { renderToString } from 'react-dom/server'
 
 export const DummyContext = createContext(null)
 
-class MyApp<P = {}> extends App<P & { html: string }> {
+export default class MyApp extends App<{ html: string }> {
   static async getInitialProps({ Component, AppTree, ctx }: AppContext) {
     let pageProps = {}
 
@@ -34,7 +34,6 @@ class MyApp<P = {}> extends App<P & { html: string }> {
   render() {
     const { Component, pageProps, html, router } = this.props
     const href = router.pathname === '/' ? '/another' : '/'
-
     const child =
       html && router.pathname !== '/hello' ? (
         <>
@@ -52,5 +51,3 @@ class MyApp<P = {}> extends App<P & { html: string }> {
     )
   }
 }
-
-export default MyApp