`wptexturize()` improvements:

* Expand the `wptexturize()` RegEx to include the list of registered shortcodes.
* Avoid backtracking after `[` chars by not filtering params in registered shortcodes. This will cause escaped shortcodes and their params to become texturized if not registered.
* Registered shortcode params will never be texturized, even when escaped.
* Move all tests involving unregistered shortcodes to a new and improved unit.
* Update one test involving HTML within shortcode params.

Props miqrogroove.
See #29557.

Built from https://develop.svn.wordpress.org/trunk@29748


git-svn-id: http://core.svn.wordpress.org/trunk@29520 1a063a9b-81f0-0310-95a4-ce76da25c4cd