Posts, Post Types: Ensure that all post stati are countable in `wp_count_posts`.

When `wp_count_posts()` is cached, it does so with all statuses defaulted to 0. The problem is however, if this is called before all plugins have registered their desired statuses, they won't have that default.

Fixes #49685.

Props obliviousharmony, SergeyBiryukov.


Built from https://develop.svn.wordpress.org/trunk@48497


git-svn-id: https://core.svn.wordpress.org/trunk@48259 1a063a9b-81f0-0310-95a4-ce76da25c4cd