Rename the buttons to be more explicit

The buttons labels should be more explicit than “Yes” and “No”. Every time we have buttons in a dialog, we should try to make their label as explicit as possible. For example, in the first dialog it could be “Cancel” and “Upgrade”, or “Cancel” and “Try again” on network errors, or “Restart now” and “Restart later” once the upgrade is over.

Parent Task: #6014 (closed)

Original created by @sajolida on 6501 (Redmine)