Block Visibility: Support non-inline Forms

[n7studios]

Summary

This PR improves compatibility with the third-party Block Visibility plugin, which adds visibility controls to Gutenberg blocks, including Kit's Form block. It allows blocks to be shown or hidden based on various conditions.

For example, users can place a Form block in a theme's footer and set it to display only on specific parts of the site, such as excluding certain Posts by Category. This addresses a reported use case where a non-inline Form needs to appear site-wide except on Posts assigned to a specific Category.

By default, Block Visibility works well with our Form block. However, due to how we defer non-inline Form scripts to the footer (to avoid layout issues), the Form script remains on the page even when Block Visibility hides the Form block, because the script has already been queued for output before Block Visibility runs on WordPress' render_block filter.

This PR improves compatibility by:

• checking if the Block Visibility plugin is active,
• if so, runs visibility checks for the Form block earlier on in the request

This prevents the non-inline Form script from being added to the footer, if the block is hidden, ensuring correct working functionality.

Testing

• testFormBlockWithNonInlineFormAndBlockVisibilityPlugin: Tests that a Form Block with a non-inline Form specified, with conditions meaning it won't display on the Page, results in the Form <script> tag not being output.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

[noelherrick]

Thanks for the detailed comments.