Ask user about deleting uploaded files when removed from message

[alya]

As discussed on CZO, if a user removes a reference to an uploaded file when editing a message, that file can still be accessed from the message's edit history. We should offer the option of deleting the file altogether in this situation, without having to do it manually via the settings menu.

For details of the modal text, the mobile app should follow the web app implementation. In-progress pull request:

• Uploads: Show modal to delete detached attachments after message edit. zulip#25764

Web app issue:

• Ask user about deleting uploaded files when removed from message zulip#25525