[FIX] product: unarchive variant archive template

Steps to reproduce:
  * Create a template with 2 variants
  * Archive one variant
  * Unarchive this same variant

--> the template is archived
This is due to commit 6a13b565cbbad89ff1c4177b171b01f30c83edf9. If the
variant is the only one, toggle_active on the variant should be
reflected on the template. The issue is that toggle active do not count
archived variant. One active variant and one archived variant are
counted as 1.
This commit make toggle_active count all variants

saas-12.3 backport of odoo/odoo#34769

note: saas-13.3 commit f36d0ce5 backported because the issue was
solved differently in 13.0 a266ff55 but it's better to have the same
code accross all version.

opw-2226294
closes #49906

closes odoo/odoo#49929

X-original-commit: c2f86f6a3998e49d1024faf41791c6341b13d54d
Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>