Remove makePublic from non-public classes

[igorschoester]

Context

We do not retrieve these classes via our YoastSEO helper. Therefor, we have no reason to expose them. By not exposing we are making it easier for ourselves to maintain code without BC breaking in the future. Although this technically counts as BC break, the code itself is not expected to be used and rather new.

Summary

This PR can be summarized in the following changelog entry:

• Remove a list of classes from being accessible via our YoastSEO classes helper.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Devs: search for the classes: they should NOT be using inside our YoastSEO()->classes() API.
• Perhaps a quick smoke test of the affected areas?
  • AI introduction things: only possible in for versions between 20.12 - 21.1, perhaps once the upcoming feature branch is merged
  • BF promotions: change the date in there and verify they still show:
    • The checklist is in the editor with WooCommerce (not our add-on 😉 )
    • The other is basically all the other place, if one works, all should work

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors (Block/Classic/Elementor/other)
• Changes should be tested on different browsers
• Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• I have added unit tests to verify the code works as intended.
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label.
• I have added my hours to the WBSO document.

Fixes #

[thijsoo]

CR + ACC 👍