Featured Image Field: Improve layout

[gigitux]

According to @jameskoster, we need to update the layout of the Featured Image Field Control layout:

I ask because out of conversations in other issues came a realisation that we might improve the design by making the 'Choose image..." button a drop zone:

Originally posted by @jameskoster in #64496 (comment)

[jameskoster]

I don't think it's 100% certain that the featured image control should adopt this design. But there should be a file or media control option in the data forms api that does.

Related to this work is updating DropZone and FormFileUpload components. There's some related discussion in #65333. This might be considered a blocker here.

[ntsekouras]

I don't think it's 100% certain that the featured image control should adopt this design. But there should be a file or media control option in the data forms api that does.

Should we close this one in favor of: #66403 then?

[gigitux]

I’d suggest keeping it open, as although the Featured Image Field control has been merged, it remains a suboptimal solution. We’ll need to improve the current layout once we have access to the appropriate API.

[jameskoster]

There's also the design discussion to be had around whether the featured image control should remain a bespoke UI outside of the post/page meta data form. Given the accessibility quandary, and additional maintenance required, I'd lean towards no, but it needs more input from @gutenberg-design.