feat(compiler): generate proper reexports in .ngfactory.ts files to not need transitive deps for compiling .ngfactory.ts files. (#13524)

Note: This checks the constructors of `@Injectable` classes more strictly.
E.g this will fail now as the constructor argument has no `@Inject` nor is
the type of the argument a DI token.

```
@Injectable()
class MyService {
  constructor(dep: string) {}
}
```

Last part of #12787
Closes #12787

modules/@angular/core/src/di/opaque_token.ts

@@ -6,8 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Injectable} from './metadata';
-
 /**
  * Creates a token that can be used in a DI Provider.
  *
@@ -30,7 +28,6 @@ import {Injectable} from './metadata';
  * error messages.
  * @stable
  */
-@Injectable()  // so that metadata is gathered for this class
 export class OpaqueToken {
   constructor(private _desc: string) {}