refactor(ivy): generate ngFactoryDef for injectables (#32433)

With #31953 we moved the factories for components, directives and pipes into a new field called `ngFactoryDef`, however I decided not to do it for injectables, because they needed some extra logic. These changes set up the `ngFactoryDef` for injectables as well.

For reference, the extra logic mentioned above is that for injectables we have two code paths:

1. For injectables that don't configure how they should be instantiated, we create a `factory` that proxies to `ngFactoryDef`:

```
// Source
@Injectable()
class Service {}

// Output
class Service {
  static ngInjectableDef = defineInjectable({
    factory: () => Service.ngFactoryFn(),
  });

  static ngFactoryFn: (t) => new (t || Service)();
}
```

2. For injectables that do configure how they're created, we keep the `ngFactoryDef` and generate the factory based on the metadata:

```
// Source
@Injectable({
  useValue: DEFAULT_IMPL,
})
class Service {}

// Output
export class Service {
  static ngInjectableDef = defineInjectable({
    factory: () => DEFAULT_IMPL,
  });

  static ngFactoryFn: (t) => new (t || Service)();
}
```

PR Close #32433

packages/core/src/render3/definition.ts

@@ -753,11 +753,11 @@ export function getBaseDef<T>(type: any): ɵɵBaseDef<T>|null {
 export function getFactoryDef<T>(type: any, throwNotFound: true): FactoryFn<T>;
 export function getFactoryDef<T>(type: any): FactoryFn<T>|null;
 export function getFactoryDef<T>(type: any, throwNotFound?: boolean): FactoryFn<T>|null {
-  const factoryFn = type[NG_FACTORY_DEF] || null;
-  if (!factoryFn && throwNotFound === true && ngDevMode) {
+  const hasFactoryDef = type.hasOwnProperty(NG_FACTORY_DEF);
+  if (!hasFactoryDef && throwNotFound === true && ngDevMode) {
     throw new Error(`Type ${stringify(type)} does not have 'ngFactoryDef' property.`);
   }
-  return factoryFn;
+  return hasFactoryDef ? type[NG_FACTORY_DEF] : null;
 }
 
 export function getNgModuleDef<T>(type: any, throwNotFound: true): NgModuleDef<T>;