[FIX] website: improve COW feature readability
[FIX] website: improve COW feature readability

This commit only re-indents the COW feature code and adds comments to
help understand its tricky parts. Also evaluate the 'no_cow' flag only
once per write.

closes odoo/odoo#28753
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo