Bug 27594: Add access to public download link for publicly-accessible uploads

Bug 27594: Add access to public download link for publicly-accessible uploads

This patch adds a link to the display of publicly-accessible uploads so
that the user can copy the public link. This will hopefully lead to
easier use of sound file uploads in the Audio Alerts system.

To test, apply the patch and go to Tools -> Upload.

- If necessary, upload a file with the "Allow public downloads"
  checkbox checked.
- Upon upload you should be shown the results of your upload in a table
  with the file details.
- In the "Public" column you should see that "Yes" is a link.
  - When you hover your mouse over the link you should see a tooltip,
    "Copy link to this file."
  - When you click the link the tooltip should say "Link copied to the
    clipboard."
  - Verify that the correct link has been copied.
- Test uploading a file which is not publicly-accessible.
  - Confirm that the information in the "Public" column says "No" and is
    not a link.

Signed-off-by: David Nind <david@davidnind.com>
Bug 27594: (QA follow-up): Use clipboard API

While the Clipboard API doesn't
have 100% coverage (https://www.caniuse.com/?search=clipboard), it has
enough coverage for the "copy" operation that it can be counted on for
use in the staff interface.

This patch removes the global copyToClipboard function and replaces it
with a call to ndavigator.clipboard.writeText() in the template.

To test, follow the previous test plan and confirm that the public
download link is still copied correctly to the clipboard.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>