[FIX] website: cast website_id to int in pagenew

Cast website_id so that if it contains more than 1 digit, we do not
browse() a tuple with each digit. For example, if we pass pagenew() the
website_id '123', this is the current behavior:
 - browse('1', '2', '3')
After this fix:
 - browse(123)

To reproduce the erroneous behavior:
 - Create at least 10 websites so that the id of this website is at
least in the double digits.
 - Create a new page within this website with a double digit id.
 - It will throw an expected singleton error.

Issue was introduced in this commit: https://github.com/odoo/odoo/commit/d6014c60acc4231a5e56d492d2a39deaf789cbe8



opw-3290571

closes odoo/odoo#121486

Signed-off-by: Romain Derie (rde) <rde@odoo.com>