[FIX] web_editor, website: avoid returning children of inactive view

Before this commit, for the following view tree:
P (active)
|
I (inactive)
|
II (active)
When calling `customize_template_get()` on 'P', it would wrongly return 'II'.
It shouldn't, since its parent 'I' is inactive.

Step to reproduce:
- Go to /shop
- Enable ecommerce categories
- Enable Collapsible Cateogories
- Disable ecommerce categories
- Collapsible categories is still shown even if its parent got archived

Test writen in 12.0 with #35154

closes odoo/odoo#35155

Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>