* Fixes `VrtNU` extractor to work with the VRT MAX site change
* Adapts `VRT`, `Ketnet` and `DagelijkseKost` extractors to the new VRT API
* Removes `Canvas` and `CanvasEen` extractors; the sites and API no longer exist
* Moves all remaining VRT-related extractors into the `vrt` module

Closes #4908
Authored by: jeroenj, bergoid, bashonly

Co-authored-by: bergoid <bergoid@users.noreply.github.com>
Co-authored-by: bashonly <88596187+bashonly@users.noreply.github.com>