Run tests in a native Node.js ESM environment (#13966)

packages/babel-register/src/nodeWrapper.ts

@@ -13,6 +13,9 @@ const internalModuleCache = Object.create(null);
 
 Module._cache = internalModuleCache;
 const node = require("./node");
+
+// NOTE: This Module._cache set is intercepted by the beforeEach hook in
+// packages/babel-register/test/index.js to install dependencies mocks.
 Module._cache = globalModuleCache;
 
 // Add source-map-support to global cache as it's stateful