Add rule to avoid redundant ternaries

[rmccue]

I've seen in a few places we have code like this:

return $foo ? true : false;

The ternary here is redundant and is actually just casting the variable to a boolean. Using an actual cast is cleaner:

return (bool) $foo;

(The reverse is true as well, return $foo ? false : true; can be replaced with return ! $foo)

[kadamwhite]

Is there a PHPCS sniff for this? @rmccue to investigate. I'm 👍 on the change proposed here

[kadamwhite]

Neither PHPCS nor WP have a sniff for this.

[rmccue]

Also nothing in the wider market :( Let's move to backlog; it's nice, but would require some custom work, so someday...