Refactor IdMap test helper to medusa-test-utils package

packages/medusa-test-utils/.babelrc

@@ -0,0 +1,9 @@
+{
+  "plugins": ["@babel/plugin-proposal-class-properties"],
+  "presets": ["@babel/preset-env"],
+  "env": {
+    "test": {
+      "plugins": ["@babel/plugin-transform-runtime"]
+    }
+  }
+}