Prevent `get_post_status()` returning `false` for attachments if the parent post has been deleted. The returned attachment post status is now passed through the `get_post_status` filter.
Add tests for `get_post_status()`.
Props peterwilsoncc, timothyblynjacobs for review.
Fixes#52326.
git-svn-id: https://develop.svn.wordpress.org/trunk@49985 602fd350-edb4-49c9-b593-d223f7449a82
