[IMP] website: add cache for _get_canonical_url_localized

This method is called at least once by lang by request. On a website of ~20
langs (e.g. on a staging of odoo.com) it improves the page speed to generate
a blog post of:
   45 0.028 0.056 with the cache
instead of
   79 0.076 0.095 without the cache

closes odoo/odoo#89709

Signed-off-by: Jérémy Kersten <jke@odoo.com>