Browser uploader in media library shows no error information

[solarissmoke]

In wp-admin/media-new.php, if you use the browser uploader, you get no information about errors.

For example if the file you upload is too large, you just get redirected to the media library with the message "Error saving media attachment." Not very helpful - and also inconsistent - because if you do exactly the same thing using the pop-up image editor (i.e., select "Add an Image" from the Upload/Insert menu while editing a post), then you do get useful error information.

I propose that if there are errors, the user should not be redirected to the Media Library. Instead Wordpress should wp_die telling them what went wrong.

[solarissmoke]

With browser uploader, don't redirect back to media library and instead tell the user what went wrong.

[solarissmoke]

Patch is a bit messy, but it tells the user what happened when something went wrong with the rowser uploader.

[dd32]

Confirmed that this is still an issue, when for example, you attempt to upload a too large a file.

Patch no longer applies.

[solarissmoke]

Patch refreshed.

[antpb]

Tested with success. This is all around a much better experience. I received the "Error saving media attachment." after a redirect to the media library page when hitting upload with no file selected.

[wonderboymusic]

In 34002:

media-new.php, when using the browser uploader, if the result of uploading is a WP_Error - wp_die() with the error, instead of redirecting with a generic error.

Props solarissmoke.
Fixes #16820.