[IMP] website: introduce cookies bar on website

With this commit, it is now possible to activate a cookies bar on a
website through the res.settings.

The cookies bar can be edited in the frontend by entering edit mode.

The cookies bar will appear until the user clicks on 'I agree'.

Part of https://github.com/odoo/odoo/pull/41294


task-2087003

closes odoo/odoo#41294

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>