This reduce memory consumption during re-builds.
```
runtime.ba93f81591909b93394f.hot-update.js.map will be removed
styles.ba93f81591909b93394f.hot-update.js.map will be removed
runtime.ba93f81591909b93394f.hot-update.json will be removed
runtime.ba93f81591909b93394f.hot-update.js will be removed
styles.ba93f81591909b93394f.hot-update.js will be removed
```
See https://github.com/webpack/webpack/issues/12947#issuecomment-812108140 and https://github.com/webpack/webpack/issues/13127
A pool of Workers is now used to process Sass render requests. This change allows multiple synchronous render operations to occur at the same time. Sass synchronous render operations can be up to two times faster than the asynchronous variant. The benefit will be most pronounced in applications with large amounts of Sass stylesheets.
The dart-sass Sass implementation will now be executed in a separate worker thread. The wrapper worker implementation provides an interface that can be directly used by Webpack's `sass-loader`.
The worker implementation allows dart-sass to be executed in its synchronous mode which can be up to two times faster than its asynchronous mode. The worker thread also allows Webpack to continue other bundling tasks while the Sass stylesheets are being processed.
All TypeScript files have been updated to pass the new eslint-based linting checks. eslint compatible disabling comments have also been added in place of the previous tslint comments.
Library code inside fesm2015/esm2015/_esm2015 directories has been downlevelled to ES2015 which will not have native async/await. As a result, code from those directories can be skipped from the additional checks as well as the downlevel processing. RxJS uses the `_esm2015` directory naming convention.
With this change we configure `webpack-dev-middleware` and `webpack-dev-server` to print errors to the console, which previously were not displayed. This is because both of these libraries log/emit errors using the logger and the compilation API.
Certain errors such as the one below, were being swallowed during `ng serve`.
```
An unhandled exception occurred: Prevent writing to file that only differs in casing or query string from already written file.
This will lead to a race-condition and corrupted files on case-insensitive file systems.
/home/circleci/ng/aio/dist/generated/docs/api/router/Routes.json
/home/circleci/ng/aio/dist/generated/docs/api/router/ROUTES.json
```
