[FIX] base: wkhtml2pdf multiple documents

Steps to reproduce:
- set up a header with company logo
- print 20 sale orders in arabic

Bug:
header disapears on most pages

Fix:
add a setting to allow users to increase the delay before printing

opw-3217155

closes odoo/odoo#121054

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>