Support rendering Media reference field as field download link

Problem/Motivation

With the existing file_download_link formatter a Media field cannot directly be rendered as a download link. One would first have to make a view mode for the Media type that uses the field_download_link to render its file. Then the Media field would render the Media item as a rendered entity using that view mode. It's just a little cumbersome.

Proposed resolution

Add a submodule with a dependency on core media. The module would provide a new field formatter called file_download_link_media. This formatter would be applicable on entity reference fields that exclusively reference media types whose allowed_field_types are file and/or image. The field formatter would essentially render the source field of the referenced media item using the existing file_download_link formatter.

User interface changes

Perhaps a message could be added to the file_download_link formatter form on a media type's manage display form. It could alert the user of this alternative.

API changes

None.

Data model changes

None.

Release notes snippet

TBD