Media, Featured Images: The media modal doesn't remember filter settings in the context of featured images

[ryan]

​https://make.wordpress.org/flow/2015/09/07/media-featured-images-setting-the-featured-image-on-an-old-post-macnchrome/

A thread on #23205 discusses featured image flow through the media modal. There are requests that the filter in the media modal remember the “uploaded to this post” filter setting independently for the featured image flow.

Considerations:

• “Uploaded to this post” requires that the image be attached to a post. Images uploaded through the media modal from the editor are attached to the post, but images uploaded directly to the media library are not attached and don’t get attached later when added to a post. We could use some API for pulling images out of post content, like we do with some other media types. See related discussions on #23041 "Images Don't Become Attached When Inserting a Gallery" and #32622 "Make the text of the Image delete AYS dialog clearer".
• If no images are attached to the post, the filter should be set to show all images.