What?

Displays a warning message if router regions are found without a data-wp-interactive attribute.

Why?

As mentioned in #71635 (comment), router regions, even nested inside a data-wp-interactive element, require both data-wp-router-region and data-wp-interactive attributes to be in place. When data-wp-interactive is missing, no warning message is emitted, causing confusion to developers (see #70883 (comment)).

How?

This PR does two things:

• Exposes the warn util from the Interactivity API as a private API.
• Uses warn to display a warning message when SCRIPT_DEBUG is true.

Testing Instructions

1. Go to the site editor.
2. Modify the homepage template and add the following HTML outside of the Query block.

   <div data-wp-router-region="region-1">Region 1.</div>
   <div data-wp-router-region="region-2">Region 2.</div>

3. Ensure "Force page reload" is disabled in the Query block.
4. Visit the homepage.
5. Open the console.
6. Hover the "Next Page" link.
7. Ensure a warning similar to this one appears on the console:

   Page "/?query-1-page=2" contains the following router regions without a 'data-wp-interactive' attribute: "region-1", "region-2".
   
   Elements with a 'data-wp-router-region' directive must also include a 'data-wp-interactive' attribute on the same element in order for these router regions to be updated correctly during navigation.