Performance/Webpack: Introduces more aggressive code-splitting and other perf improvements (#18544)

* Performance/Webpack: Introduces more aggressive code-splitting and other perf improvements
- Introduces dynamic imports for built-in plugins
- Uses dynamic imports for various packages (rst2html, brace)
- Introduces route-based dynamic imports
- Splits angular and moment into separate bundles

scripts/webpack/webpack.hot.js

@@ -42,41 +42,44 @@ module.exports = merge(common, {
 
   optimization: {
     removeAvailableModules: false,
+    runtimeChunk: false,
     removeEmptyChunks: false,
-    splitChunks: false,
+    splitChunks: false
   },
 
   module: {
-    rules: [
-      {
+    rules: [{
         test: /\.tsx?$/,
         exclude: /node_modules/,
-        use: [
-          {
-            loader: 'babel-loader',
-            options: {
-              cacheDirectory: true,
-              babelrc: false,
-              plugins: [
-                [require('@rtsao/plugin-proposal-class-properties'), { loose: true }],
-                'angularjs-annotate',
-                '@babel/plugin-syntax-dynamic-import', // needed for `() => import()` in routes.ts
-                'react-hot-loader/babel',
-              ],
-              presets: [
-                [
-                  '@babel/preset-env',
-                  {
-                    targets: { browsers: 'last 3 versions' },
-                    useBuiltIns: 'entry',
+        use: [{
+          loader: 'babel-loader',
+          options: {
+            cacheDirectory: true,
+            babelrc: false,
+            plugins: [
+              [require('@rtsao/plugin-proposal-class-properties'), {
+                loose: true
+              }],
+              'angularjs-annotate',
+              '@babel/plugin-syntax-dynamic-import', // needed for `() => import()` in routes.ts
+              'react-hot-loader/babel',
+            ],
+            presets: [
+              [
+                '@babel/preset-env',
+                {
+                  targets: {
+                    browsers: 'last 3 versions'
                   },
-                ],
-                '@babel/preset-typescript',
-                '@babel/preset-react',
+                  useBuiltIns: 'entry',
+                  modules: false
+                },
               ],
-            },
+              '@babel/preset-typescript',
+              '@babel/preset-react',
+            ],
           },
-        ],
+        }, ],
       },
       {
         test: /\.scss$/,
@@ -86,7 +89,9 @@ module.exports = merge(common, {
           {
             loader: 'postcss-loader',
             options: {
-              config: { path: __dirname + '/postcss.config.js' },
+              config: {
+                path: __dirname + '/postcss.config.js'
+              },
             },
           },
           {
@@ -108,6 +113,7 @@ module.exports = merge(common, {
       template: path.resolve(__dirname, '../../public/views/index-template.html'),
       inject: 'body',
       alwaysWriteToDisk: true,
+      chunksSortMode: 'none'
     }),
     new HtmlWebpackHarddiskPlugin(),
     new webpack.NamedModulesPlugin(),