BREAKING CHANGE:
Differential loading support has been removed. With Angular no longer supporting IE11, there are now no browsers officially supported by Angular that require ES5 code. As a result, differential loading's functionality for creating and conditionally loading ES5 and ES2015+ variants of an application is no longer required.
The worker pool for differential loading and i18n processing is now managed by the `piscina` dependency. This dependency is already used within the recently added JavaScript optimizer refactoring and reduces both the number of direct dependencies and amount of code to setup the worker pools.
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.
Stopping the workers can be a potentially lengthy process with a multi-stage approach based on the state of the worker. This can cause lengthy blocking of the build. This change allows the shutdown to happen in parallel to the remainder of the build.
