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`.
`ngc` would look for flat module resources relative to the flat module index.
`ngc` now looks for flat module resources relative to the `.d.ts` file that declarates
the component.
Fixes#15221
PR Close#15367
Miško Hevery
Tobias Bosch
Chuck Jazdzewski
Jason Aden