feat: Add currency module and remove currency models from region and pricing modules (#6536)

What:
- Creates a new currency module
- Removes currency model from the pricing module
- Removes currency model from region module

packages/pricing/src/models/index.ts

@@ -1,4 +1,3 @@
-export { default as Currency } from "./currency"
 export { default as MoneyAmount } from "./money-amount"
 export { default as PriceList } from "./price-list"
 export { default as PriceListRule } from "./price-list-rule"