Add select2 to all select fields in WordPress Admin

wp-admin-select2.php

<?php

function enqueue_select2_jquery() {
    wp_register_style( 'select2css', '//cdnjs.cloudflare.com/ajax/libs/select2/3.4.8/select2.css', false, '1.0', 'all' );
    wp_register_script( 'select2', '//cdnjs.cloudflare.com/ajax/libs/select2/3.4.8/select2.js', array( 'jquery' ), '1.0', true );
    wp_enqueue_style( 'select2css' );
    wp_enqueue_script( 'select2' );
}
add_action( 'admin_enqueue_scripts', 'enqueue_select2_jquery' );

function select2jquery_inline() {
    ?>
<style type="text/css">
.select2-container {margin: 0 2px 0 2px;}
.tablenav.top #doaction, #doaction2, #post-query-submit {margin: 0px 4px 0 4px;}
</style>
<script type='text/javascript'>
jQuery(document).ready(function ($) {
    if( $( 'select' ).length > 0 ) {
        $( 'select' ).select2();
        $( document.body ).on( "click", function() {
             $( 'select' ).select2();
          });
    }
});
</script>
    <?php
 }
add_action( 'admin_head', 'select2jquery_inline' );