Change the 'WP_Theme_JSON_Data_Gutenberg' class directory

[Mamaduka]

What?

This is a follow-up to #46750.

PR moves the WP_Theme_JSON_Data_Gutenberg bundled class into the correct directory and matches PHPDoc-blocks to the core.

Why?

The class is always bundled in the plugin and doesn't depend on the support WP version.

Testing Instructions

PR is just changing file directories. Confirm the are no PHP errors/notices when running this branch.

[oandregal]

Thanks for this. Unlike the other two classes, this one didn't receive any other update since it landed. It sounds like it can be beneficial to "let it go": remove it once the minimum WordPress version of Gutenberg is raised to 6.1. We did the same with other classes we did not update: WP_Theme_JSON_Schema, for example.

[Mamaduka]

@oandregal, the core class will use WP_Theme_JSON instead of WP_Theme_JSON_Gutenberg, wouldn't that be a problem?

P.S. I noticed this class in the wrong dir when I started working on dropping the WP 6.1 support.

[Mamaduka]

@oandregal, I confirmed that new block features like "position" stop working (WP 6.1.) without bundling this class in the plugin.

The core version uses WP_Theme_JSON, while the plugin code should always use WP_Theme_JSON_Gutenberg to access the latest features.

Edit: I will merge this minor change to unblock #50079. I'm happy to do a follow-up if there's a different way to solve the block position support issue.

[oandregal]

Oh, you are absolutely right, @Mamaduka It uses the class internally, so it needs to point to the Gutenberg one. Thanks for taking care of it.