Improve tests for `is_email_address_unsafe()`.

* Move to a separate file for better organization and method names.
* Use a `dataProvider` when appropriate, for better readability.
* Add a test for splitting the banned domain list on line breaks.

See #20459, #21730.
Built from https://develop.svn.wordpress.org/trunk@32638


git-svn-id: http://core.svn.wordpress.org/trunk@32608 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.3-alpha-32637';
+$wp_version = '4.3-alpha-32638';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.