Create unique route path for og under group routes (#47985)
### What
When using dynamic metadata image rouets (such as `opengraph-image.js`)
under group routes, the generated urls were still normalized. In this
case it might have conflicts with those ones not under group routes. For
instance `app/(post)/opengraph-image.js` could have same url with
`/app/opengraph-image.js`. In reality we want them to be different
route, unlike layout or pages.
### How
So when we found `()` or `@` signs from the metadata image urls, we'll
generate a unqiue suffix (`-\d{6}`) and append to the generated url. So
they can be isolated from the ones are not under special convention
routes.
Closes NEXT-937
