chore(): Reorganize modules (#7210)

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

packages/modules/tax/src/index.ts

@@ -0,0 +1,13 @@
+import { initializeFactory, Modules } from "@medusajs/modules-sdk"
+import { moduleDefinition } from "./module-definition"
+
+export * from "./models"
+export * from "./services"
+
+export const initialize = initializeFactory({
+  moduleName: Modules.TAX,
+  moduleDefinition,
+})
+export const runMigrations = moduleDefinition.runMigrations
+export const revertMigration = moduleDefinition.revertMigration
+export default moduleDefinition