[FIX] mail: send email from CRM using a template

When sending emails from CRM, you can save the mail as a new template.
Despite having selected the desired recipients, the mails sent will not
have any recipients.

Steps to reproduce:
1. Install CRM and open the app
2. Trigger the list view of the pipeline
3. Select any opportunities, go to Action and click on 'Send email'
4. Give a subject to the email and click on 'SAVE AS NEW TEMPLATE'
5. Send the email
6. Go to emails, there are no recipients for the emails generated

Solution:
Set the `use_default_to` to true by default when using the 'SAVE AS NEW
TEMPLATE' button

opw-2827177

closes odoo/odoo#92859

X-original-commit: 79791461
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>
Signed-off-by: Guillaume Merlin (megu) <megu@odoo.com>