File Field design update: Multiple file fields

Problem/Motivation

This is a followup of #2113931: File Field design update. The designs update for the file/image fields contained a proposal for a field with multiple files:

The design has some issues that need to be addressed.

• The table header is important for the cases where you have multiple columns, like the weight field and the display checkbox. We probably can't remove that.
• The tabledrag is missing, this feature is important and should be incorporated in the design.
• The 'Show row weights' link is missing as well.
• When adding multiple files, the label and the upload field are quite far apart. We need a way to show users where a field starts and where the field ends.

Proposed resolution

To be determined.

Remaining tasks

• Update the design to include all elements we need.
• Implement the updated design.

User interface changes

API changes

Data model changes

Release notes snippet