Move B2B models from core to feature lib

[Platonn]

Our very core model like Order were lately (in last 2 months) polluted with b2b-related properties (i.e. order.costCenter) . This prevents us from moving b2b-related types (i.e. CostCenter) from core to the feature lib, because core would depend then on the feature lib (Order would depend on CostCenter).

We see a hope in the ongoing ticket for Extensible types (aka Types augmentation) #7940

This will allow for keeping thin Order in the core lib, but in the my-account lib import this TS interface and re-declare it with adding new properties (like costCenter: CostCenter). Then the core lib won't depend on the my-account lib.

It's a follow up of #8423
Blocked by #7940

[marlass]

Actually Order is more of an checkout lib responsibility so it should not be moved to my-account. However this task still applies for other models that are primarly used in my-account and also needed in B2B Checkout. Then the my-account properties of those models should be moved there utilizing type augmentation.