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/currency/mikro-orm.config.dev.ts

@@ -0,0 +1,8 @@
+import * as entities from "./src/models"
+
+module.exports = {
+  entities: Object.values(entities),
+  schema: "public",
+  clientUrl: "postgres://postgres@localhost/medusa-currency",
+  type: "postgresql",
+}