Expose metadata types (#47630)
### What?
- Besides existing `Metadata` type, expose `ResolvingMetadata` and `ResolvedMetadata` to `'next'`.
- Group `Robots` / `Sitemap` / `Manifest` these dynamic data routes types as `MetadataRoute` type and expose to `'next'`
### Why?
Allow users to type the more API easily, and grouping them to avoid type conflicts (e.g. we have `Robots` in metadata interface field, `MetadataRoute.Robots` can avoid conflicts)
### How?
Closes NEXT-908
