REST API: Regenerate fixure schema after introduction of new endpoints.

This fixture schema ensures `wp-api-generated.js` doesn't change when running tests in local dev environments.

Merges [43851] from the 5.0 branch to trunk. `wp-api-generated.js` generated based on current trunk.
Props danielbachhuber.
Fixes #45196.

Built from https://develop.svn.wordpress.org/trunk@44217


git-svn-id: https://core.svn.wordpress.org/trunk@44047 1a063a9b-81f0-0310-95a4-ce76da25c4cd