Clean up old WP->public_query_vars and WP->private_query_vars

[prettyboymp]

There are some old non-working public_query_vars still in the WP class that should be cleaned up.

• posts - broken 10 years ago ​http://core.trac.wordpress.org/changeset/182/trunk/blog.header.php
• search - hasn’t done anything since wp_query was created
• calendar - don’t see support since ‘b2’
• pb - don’t see support since ‘b2’
• static - only used in determining if is_page, though it no longer works correctly, added ​http://core.trac.wordpress.org/changeset/1527/trunk, but functionality was partially changed the next commit

Also, since 'post_type' is now a public_query_var, it can be removed from the private_query_vars.

[nacin]

Keep in mind it may be worth holding onto some of these as reserved terms for future use, like search.

[nacin]

I don't care much about static, pb, or even calendar, but I think it'd make sense for search and posts to remain reserved. (I wonder what pb was for.)

Going to clean up post_type and leave the others alone for now.

[nacin]

In 27738:

WP class: Remove duplication of the post_type query var, also specified as a public QV.

props prettyboymp.
fixes #23862.

[nacin]

Alright, this actually broke a canonical unit test. (The noRewrite ?post_type=fake-cpt&p=1 one.)

WP::parse_request() parses public query vars and then parses private query vars. But in between there, it discards any post types that aren't publicly queryable. The canonical tests leverage WP::main() directly, and thus private query vars have outsized influence... It's kinda tough to explain, and was not fun to track down.

Anyway, as this was ostensibly for cleanup, and it clearly causes some side effects, I'm reverting.

[nacin]

In 27768:

Revert [27738] as the patient exhibited side effects. see #23862.

[nacin]

#27549 and #27547 — this definitely breaks things, in this case the admin which uses wp() and thus private query variables directly.

So at least for the post_type query variable, which is a particularly special case in the WP class, it's *not* invalid for it to be listed in public *and* private query variables.