Add a warning message before overwriting assets in Files and Uploads

[ormsbee]

There is currently no warning message when you are about to overwrite existing files on Studio's File and Uploads page.

Let's add a warning in a modal, in the same style as the delete confirmation (including the warning triangle):

Modal Text

Title: Overwrite Files

Text: The following files will be overwritten:

This should then be followed by an <ul> of files that would be overwritten, in alphabetical order by file name.

The buttons should be "Overwrite" and "Cancel".

Acceptance Criteria:

• This new modal should only trigger when a user uploads one or more files that would overwrite existing files in File and Uploads.
• Clicking on the "Overwrite" button will cause those files to get overwritten.
• Clicking on the "Cancel" button or closing the modal will stop those files from being overwritten.

Edge case: If there are a mix of files where some of them would overwrite and some wouldn't, and the user hits "Cancel", the files that are not overwrites should still get uploaded. For example, say we have the following situation:

• The files 1.webp and 2.webp exist in Files and Uploads.
• The user uploads new files 1.webp, 2.webp, 3.webp, 4.webp.
• The modal dialog triggers, and the user hits "Cancel"

In the above scenario, 3.webp and 4.webp should still get uploaded. The user is canceling the action of overwriting the existing files, but is not canceling the entire operation.

[github-actions]

Thanks for your submission, @openedx/open-edx-project-managers will review shortly.

[tecoholic]

@ormsbee This is being handled in openedx/edx-platform#33493 and openedx/studio-frontend#384, with a different UI (which I think can be adapted to match the vision here).

[ormsbee]

@tecoholic: I didn't realize this was already being implemented. If there have already been product/UX input into that ticket, please feel free to ignore this one.

[tecoholic]

@ormsbee The UX you were suggesting was better suited than the one we had, which handled only 1 file. So we went with your suggestion. :)