The location of the html output from the_post_thumbnail();

Use the filter post_thumbnail_html (source):

function wpse_195454_post_thumbnail_html( $html ) {
    if ( $html )
        $html="<span class="wrap">" . $html . '</span>';
    return $html;
}

add_filter( 'post_thumbnail_html', 'wpse_195454_post_thumbnail_html' );