Add admin email verification screen. Shown every six months after an admin has logged in.

Also includes WPCS fixes for wp-login.php.

Props andraganescu, boemedia, lessbloat, azaozz.
See #46349.
Built from https://develop.svn.wordpress.org/trunk@45757


git-svn-id: http://core.svn.wordpress.org/trunk@45568 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,14 +13,14 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45756';
+$wp_version = '5.3-alpha-45757';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
  *
  * @global int $wp_db_version
  */
-$wp_db_version = 44719;
+$wp_db_version = 45744;
 
 /**
  * Holds the TinyMCE version