feat(build): webpack@5 and webpack-dev-server@4 (#7826)

SwaggerUI is now built using `webpack@5`, with dev support for `webpack-dev-server@4`
- ES Module output bundle path now points to `swagger-ui-es-bundle-core`, which does not include dependencies
- No change to CommonJS output bundle or path
- Now uses Asset Modules, which replaces `file-loader`, `raw-loader`, and `url-loader`
- Removed unused rules/loaders for `.woff | .woff2 | .ttf | .eot` fonts and html
- Node polyfills are no longer bundled with `webpack@5`, and must be loaded separately and/or use `resolve.fallback`. 
As an example, SwaggerUI loads `process`, `buffer`, and `stream-browserify` as `devDependencies` in order to build development and production bundles.

SwaggerUI-React
- Now imports `swagger-ui-es-bundle-core`, and similarly outputs `swagger-ui-es-bundle-core` to its `dist` directory

Dev notes:
- Order of execution matters for the production npm build scripts. `build-stylesheets` needs to get built first, 
then cleanup of any empty artifacts, before building the various production bundles
- `Dev-helpers` now relies on `HTMLWebpackPlugin` to inject css and bundle files

webpack/es-bundle-core.babel.js

@@ -29,9 +29,10 @@ const result = configBuilder(
       ],
     },
     output: {
-      globalObject: "this",
-      library: "SwaggerUIBundle",
-      libraryTarget: "commonjs2",
+      library: {
+        type: "commonjs2",
+        export: "default",
+      },
     },
     plugins: [
       new DuplicatesPlugin({