Improved approach to comment metering fix

[claudiulodro]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Note: This is a hotfix

A different approach than #3057 for the same issue. This should have much smaller potential side effects than modifying the global $wp_query object.

How to test the changes in this Pull Request:

Basically the same testing instructions as #3057

1. Add a membership plan and set it to restrict all posts. Set up a metered wall that gives anonymous readers 1 pageview and registered readers 1 pageview. Make one or more comments on a post.
2. Before applying this patch, visit the post as an anonymous reader and/or free registered user. Observe no comments are shown on the post.
3. Apply this patch.
4. Visit the post as an anonymous reader and confirm comments are shown. Visit a different post as an anonymous reader and confirm you're stopped by the wall.
5. Visit the post as a free registered reader and confirm comments are shown. Visit a different post as a free registered reader and confirm you're stopped by the wall.
6. Visit multiple posts as a paid reader and confirm you have access to all articles.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[claudiulodro]

Thanks for the speedy review! I've tested on staging and client sites, and this approach seems stable, so I'm going to merge.

[matticbot]

🎉 This PR is included in version 3.6.10 🎉

The release is available on GitHub release

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[matticbot]

🎉 This PR is included in version 3.7.0-alpha.4 🎉

The release is available on GitHub release

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