Improve some post status related documentation

[ericlewis]

I'm learning about post statuses, updating related documentation along the way.

[ericlewis]

In attachment:30230.diff​, update incorrect documentation and expand where clarity is helpful.

[wonderboymusic]

In 30155:

Improve some post_status-related documentation.

Props ericlewis.
See #30230.

[wonderboymusic]

Re-add commit if you do more work here

[DrewAPicture]

In 30284:

Fix the syntax for some status-related documentation introduced in [30155].

• Variables in DocBlocks should be backtick-escaped
• Parameter and return types should be as specific as possible
• @param types and variables should align with each other, but not intentionally with the @return description

See #30230.

[DrewAPicture]

Let's call this fixed and open new tickets for specific, newly-discovered issues with documentation.