manually setup module transforms so to support async imports in webpack (#44413)

packages/kbn-babel-preset/package.json

@@ -6,6 +6,7 @@
   "dependencies": {
     "@babel/plugin-proposal-class-properties": "^7.5.1",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
+    "@babel/plugin-transform-modules-commonjs": "^7.5.0",
     "@babel/preset-env": "^7.5.5",
     "@babel/preset-react":"^7.0.0",
     "@babel/preset-typescript": "^7.3.3",

packages/kbn-babel-preset/webpack_preset.js

@@ -24,12 +24,15 @@ module.exports = () => {
         require.resolve('@babel/preset-env'),
         {
           useBuiltIns: 'entry',
-          modules: 'cjs',
+          modules: false,
           corejs: 3,
         },
       ],
       require('./common_preset'),
     ],
-    plugins: [require.resolve('@babel/plugin-syntax-dynamic-import')],
+    plugins: [
+      require.resolve('@babel/plugin-transform-modules-commonjs'),
+      require.resolve('@babel/plugin-syntax-dynamic-import'),
+    ]
   };
 };