Use _deprecated_argument() on get_bloginfo()

[nacin]

_deprecated_argument() (#11386) is flexible enough to be used to mark deprecated values of function arguments, not just arguments themselves.

We should use it to mark get_bloginfo('siteurl') and get_bloginfo('home') as deprecated. Patch also changes any uses of those in core to 'url'.

This ticket and patch assumes that the final patch of #11386 is committed first, which simplifies _deprecated_argument() a bit and makes the function a bit more flexible.

(Also related, #10805, marking user levels as deprecated.)

[nacin]

Forgot to mention, patch does not update an instance of get_bloginfo('siteurl') that is addressed in #11607. That would need to be committed before or with this, otherwise we'll be triggering deprecated errors on every blog (unless a default filter is removed).

[westi]

Looks good.

Going to go with a simpler change in get_bloginfo as I think it is more readable and affects less of the code flow.

[westi]

(In [12587]) Use _deprecated_argument() in get_bloginfo() and then don't pass deprecated argument to get_bloginfo(). Fixes #11652 props nacin.

[westi]

(In [12589]) Don't pass deprecated argument to get_bloginfo() in the classic theme. See #11652 props nacin.