Vendor @vercel/og and expose ImageResponse (#47657
### What?
This PR vendors @vercel/og and export `ImageResponse` from
`next/server`. When you render a opengraph image the below code snippets
will be legit:
```tsx
import { ImageResponse } from 'next/server'
export default function og() {
return new ImageResponse(<div style={{ width: '100%', height: '100%' }}>hello</div>)
}
```
### Why?
To make development more easier, user can directly use `@vercel/og`
Image Response with nextjs instead of install it and use it. This makes
building metadata icons, og or twitter images more convenient.
### How?
Closes NEXT-899
