This provides more flexibility when writing tests and benefits from running in a front-end context which is necessary for some tests like checking that updates are supported. Additionally, this provides a more robust interface for developers who want to integrate with Site Health tests.
Because the `wp/v2` endpoint is reserved for modeling core entities, site health is registered in its own `wp-site-health/v1` namespace.
The existing ajax actions have been maintained for backward compatibility.
Props Clorith, chrisvanpatten, afragen, pokhriyal, TimothyBlynJacobs.
Fixes#48105.
git-svn-id: https://develop.svn.wordpress.org/trunk@49154 602fd350-edb4-49c9-b593-d223f7449a82