[change:ux] Show subnet division rule organization field only if subnet organization field is set to shared

[nemesifier]

In subnet > add, we should not show the subnet division rule organization field if the subnet has an organization set because it would be redundant, we have to ensure the system automatically sets the organization.

The second organization field in this case can just be hidden with JS.
Automatically filling the organization field on the subnet division rule can be done at model level if it isn't already handled.