This is needed as the typescript no longer elides type reexports
in the generated code when using transformers.
A nice side effect is that this make summaries shorter and produces
less reexports as we rollup reexports.
PR Close#18788
This also allows to customize the filePaths in `.ngsummary.json` file
via the new methods `toSummaryFileName` and `fromSummaryFileName`
on the `CompilerHost`.
Allows to inherit ctor args, lifecycle hooks and statics from a class
in another compilation unit.
Will error if trying to inherit from a class in another compilation unit
that has an `@Component` / `@Directive` / `@Pipe` / `@NgModule`.