Generated factory shims can import from @angular/core. However, we have
special logic in place to rewrite self-imports when generating code for
@angular/core.
This commit leverages the new standalone ImportRewriter interface to
properly rewrite imports in generated factory shims. Before this fix,
a generated factory file for core would look like:
```typescript
import * as i0 from './r3_symbols';
export var ApplicationModuleNgFactory = new ɵNgModuleFactory(...);
```
This is invalid, as ɵNgModuleFactory is just NgModuleFactory when imported
via r3_symbols.
FW-881 #resolve
PR Close#27998
6003145422