Change comment confirmation message based on approval settings

[DavidCramer]

As mentioned in #797 (comment) and #862 (comment)
The message indicated "..subject to moderation".
This message should be adjusted based on the moderation settings.
An indication of refresh times should also be mentioned.

[westonruter]

Code in question:

https://github.com/Automattic/amp-wp/blob/215860d618cc114d37f17f8efb477e6b5e3ccc40/includes/class-amp-theme-support.php#L360-L376

We should make the submit-success also contain a <template type="amp-mustache">. Then the message could say if the newly posted comment is actually moderated or not. Currently the success is just sent with success data without any data. But if this were changed to have a message like then the template can be added to render it.

In regards to the refresh time, we won't know what interval the amp-live-list is using in the theme. So if not moderated, then for now it should probably just say it will be available soon.

[csossi]

verified in QA (dev/paired/legacy)