Allow downloading DAM attachments to user's website

[abaicus]

What problem does this address?

Right now, we treat DAM attachments as we do with offloaded images (they are available to download to the user's website on the media page when switching to the list layout).

We should allow users to download them to the website and use them as plain attachments, how we do for the offloaded images.

What is your proposed solution?

• Allow processing these attachments through the rollback process and pull them to the user's website;
• Remove the DAM import flag we use right now after rollback: https://github.com/Codeinwp/optimole-wp/blob/master/inc/dam.php#L148
• Make sure we replace the URLs in the website content;

Will this feature require documentation? (Optional)

None