Avoid using user/session info for nonce verification

[heavyweight]

When a user is logged in to the site the nonce verification fails. This is because the nonce is created using the user data, and verified using user data which might not be available. This is due to the way the comment form is posted.

Fixes #32552

Related work
D156337-code

Proposed changes:

• To fix the nonce verification errors, the way we create and verify the nonce has been changed now to rely on user data.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• In incognito window login to wordpress.com and wp-admin of the site
• Verify that the original issue is reproducible on your site
• Sync this PR to an atomic site using rsync or the beta plugin
• Navigate to a post and try to post a comment
• Verify that the comment is posted without any nonce verification errors

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the fix/verbum-nonce-verification branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack fix/verbum-nonce-verification
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

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• ✅ Add changelog entries to affected projects
  

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Jetpack plugin:

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[heavyweight]

Closing in favor of #38554