Purpose
=======
A field `use_google_gmail_service` has been used in stable to define
a mail server which use Gmail authentication.
But now that the fields `smtp_authentication` exists, we want to use it
to simplify the mail server form view. For the incoming mail server,
the field `server_type` will be used for the same purpose.
Add a new field to have the option to install `google_gmail` in the
main settings page.
Task-2170676
closesodoo/odoo#83413
Related: odoo/upgrade#3199
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>