Add PrePublish upsell to bring Zapier integration to attention

[leonidasmi]

Context

• We want to add a Zapier upsell in the Pre-Publishing sidebar when Premium is not active

Summary

This PR can be summarized in the following changelog entry:

• Adds a Zapier upsell in the Pre-Publishing sidebar when Premium is not active.

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:

• When publishing a post/page/CPT in the block editor and Premium is not active (or not even installed):

• In the post-publishing sidebar, the following upsell should appear:

• The Unlock with Premium button should have a https://yoa.st/get-zapier-prepublish shortlink (with added params).

• The Connect Yoast SEO with Zapier link should go to the https://yoa.st/about-zapier shortlink (with added params).

• When Premium is active, follow the Test Instructions of https://github.com/Yoast/wordpress-seo-premium/pull/3690.

Also:

• On classic editor and Elementor editor, smoke test that posts are published without console errors.

Relevant test scenarios

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

Test instructions for QA when the code is in the RC

• [x] QA should use the same steps as above.

Impact check

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

• Confirm that when Premium is installed and the Zapier integration is enabled in settings but not connected, we show the Premium Zapier sidebar item in pre-publish. When the Zapier integration is NOT enabled, we dont show that sidebar item
• Confirm that when Premium is installed, and the Zapier integration is enabled and it is connected, then we don't show that sidebar item or the upsell.

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

• [x] I have tested this code to the best of my abilities
• [ ] I have added unittests 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.
• [x] I have written this PR in accordance with my team's definition of done.

Fixes PC-7