Display custom statuses in post states

[WPprodigy]

Closes #395

Custom post statuses has enough hacks as-is, let's adhere to core APIs and standards when we can :)

Instead of adding an extra column to the post list that takes up valuable space, let's follow core's UI and display custom statuses just like other statuses are shown in WP.

For some context, here is what is done in WP core: https://github.com/WordPress/WordPress/blob/dd4d98a368ca1d617adfaaef9b2937c60464ac4a/wp-admin/includes/template.php#L2100-L2170. Of note, I followed the same rules by letting core continue to handle some statuses specially, and by not showing the status when a specific post status is filtered.

It will also smartly handle cases where EF has changed a core statuses name (like pending). Thanks to the use of array keys, it'll override the default status display name with our custom ones.

Testing

Apply the patch and try out different post statuses, post types, etc.

---

Preview

[cojennin]

Hey great! Thanks for carrying the torch on this, I was giving it a shot with #561 but got side tracked. Definitely makes more sense

[cojennin]

A couple PHPCS issues that need fixing (can ignore anything that starts with Line indented incorrectly;, the whole file is indented incorrectly), once those are addressed it's good to go

[cojennin]

Looks good