Add media library support

The media library integration only works for a single file. We have a media field in which we can upload multiple images. This works fine with the default widget. A system dialog opens and we can upload multiple images at once. We have customers that (want to) upload a lot of large image files at once and they might encounter issues (e.g. server limits). To better support this it would be nice if we can use the File Resumable Upload module.

If we enable the dev version the module, including the work from this issue, the multiple file upload is replaced by the interfaces provided by this module. But then both the drop area and the system dialog via the Browse button only support one file at a time.

Thank you very much anrikun! Since this one was merged let's start separate follow up issues.

Created 🐛 Media library integration does not work well for fields that accept multiple values Active to follow up on the issue with multiple valued fields.

Automatically closed - issue fixed for 2 weeks with no activity.