REST API: Add the `supports` property to the Post Type response object.

Includes a new `supports` property in the response object and schema for the `/types` endpoints for users with the `edit_posts` capability for the given post type. The `supports` property returns an object of the features the given post type *supports*.

Props timmydcrawford, tyxla.
Fixes #39033.

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git-svn-id: https://core.svn.wordpress.org/trunk@39587 1a063a9b-81f0-0310-95a4-ce76da25c4cd