[IMP] extract_api: document the new API version

We have introduced a second version of the Extract API that adds the IAP
account token to the `get_result` and `validate` routes.

There are also other changes in this commit:
 - The deprecated stuff has been removed as it's been deprecated for a
   while and won't be supported anymore in the future.
 - The `status` table of the `get_result` route has been added as it was
   missing for some reason.
 - The documentation regarding the `/validate` routes have been removed
   for security reasons.

closes #6250

Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>

Author: lobaudoux