[SiOC - customer creation] Order editing form: disable editing access for customer and addresses for subscription orders

[jaclync]

Ref: pdfdoF-4Rj-p2#comment-6031

States

Set "customer account required" state to true and "customer is editable" state to false if the order has at least one subscription. Otherwise, set "customer account required" state to false and "customer is editable" state to true.

Save CTA

Event though we're disabling the customer section for subscription orders, it'd still be nice to handle this - when the "customer account required" state is true and there's no customer ID & email set, the Save CTA is disabled.

The Save CTA is enabled when any of the customer details change.

[dangermattic]

🚫 Please add a type label (e.g. type: enhancement) and a feature label (e.g. feature: stats) to this issue.