chore(): Reorganize modules (#7210)

**What**
Move all modules to the modules directory

packages/modules/sales-channel/src/module-definition.ts

@@ -0,0 +1,13 @@
+import { ModuleExports } from "@medusajs/types"
+import { SalesChannelModuleService } from "@services"
+
+import loadConnection from "./loaders/connection"
+import loadContainer from "./loaders/container"
+
+const service = SalesChannelModuleService
+const loaders = [loadContainer, loadConnection] as any
+
+export const moduleDefinition: ModuleExports = {
+  service,
+  loaders,
+}