This helps ensure we use the same tsconfig.json file for all compilations.
Next steps are to make it the same tsconfig.json file used by the editor
PR Close#20964
The private classes `ApplicationRef_`, `PlatformRef_`, `JSONPConnection_`, `JSONPBackend_`, `ClientMessageBrokerFactory_`, `ServiceMessageBroker_`, `ClientMessageBroker_` and `ServiceMessageBrokerFactory_` have been removed and merged into their public equivalents.
The size of the minified umd bundles have been slightly decreased:
| package | before | after |
| -------------------|------------|------------|
| core | 217.791 kb | 217.144 kb |
| http | 33.260 kb | 32.838 kb |
| platform-webworker | 56.015 kb | 54.933 kb |
PR Close#19143
