Refine the display of the comment approval notification opt-in confirmation message

[johnbillion]

Follow-up to #52406.

The confirmation message shown to a user after they opt-in to receiving a notification of their pending comment's approval is currently displayed inline with a preview of their comment.

This means the display of this confirmation message is only shown if the user opts in within 10 minutes of posting their comment. If they take longer than 10 minutes then their opt-in is respected but they see no confirmation message.

As mentioned in the comments in 7:ticket:52406 10 minutes is likely long enough but no research was done.

Let's identify if this functionality needs to be improved. Options:

• Extend the time limit further. This needs to take into consideration #49956.
• Disconnect the display of the confirmation message from the comment preview, and always show a confirmation message. Would need to take into consideration the cache headers on the page.
• Fix the comment spam problem some other way and remove the time limit.
• Do something else.
• Do nothing and leave it as-is.

[ryokuhi]

Moving it to 5.8 after discussion during the Accessibility Team's bugscrub.

[johnbillion]

This is dependent on #33717 going back in.

[joedolson]

Moving this to Future Release. Need to monitor #33717 and follow up if it is re-committed, but don't need to keep reviewing it every week...