Use Symfony Request for core includes

Part of #1998638: [Meta] Refactor raw PHP variables (e.g $_SERVER, $_REQUEST, $_GET, $_POST) with Symfony Request object

The following files need to be converted:

• core/includes/ajax.inc
• core/includes/batch.inc
• core/includes/bootstrap.inc
• core/includes/common.inc
• core/includes/errors.inc
• core/includes/form.inc
• core/includes/install.core.inc
• core/includes/install.inc
• core/includes/language.inc
• core/includes/mail.inc
• core/includes/pager.inc
• core/includes/session.inc
• core/includes/tablesort.inc
• core/tests/bootstrap.php