`Stream` will be qualified as `AK::Stream` until we remove the
`Core::Stream` namespace. `IODevice` now reuses the `SeekMode` that is
defined by `SeekableStream`, since defining its own would require us to
qualify it with `AK::SeekMode` everywhere.
And make it capable of printing to any Core::Stream.
This is useful on its own and can be used in a number of places, so move
it out and make it available as JS::print().
