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/compiler/src/injectable_compiler_2.ts

@@ -6,10 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {InjectFlags} from './core';
 import {Identifiers} from './identifiers';
 import * as o from './output/output_ast';
-import {R3DependencyMetadata, R3FactoryDelegateType, R3FactoryMetadata, compileFactoryFunction} from './render3/r3_factory';
+import {R3DependencyMetadata, R3FactoryDelegateType, compileFactoryFunction} from './render3/r3_factory';
 import {mapToMapExpression, typeWithParameters} from './render3/util';
 
 export interface InjectableDef {
@@ -22,7 +21,6 @@ export interface R3InjectableMetadata {
   name: string;
   type: o.Expression;
   typeArgumentCount: number;
-  ctorDeps: R3DependencyMetadata[]|'invalid'|null;
   providedIn: o.Expression;
   useClass?: o.Expression;
   useFactory?: o.Expression;
@@ -38,7 +36,7 @@ export function compileInjectable(meta: R3InjectableMetadata): InjectableDef {
     name: meta.name,
     type: meta.type,
     typeArgumentCount: meta.typeArgumentCount,
-    deps: meta.ctorDeps,
+    deps: [],
     injectFn: Identifiers.inject,
   };
 
@@ -67,19 +65,22 @@ export function compileInjectable(meta: R3InjectableMetadata): InjectableDef {
     } else if (useClassOnSelf) {
       result = compileFactoryFunction(factoryMeta);
     } else {
-      result = compileFactoryFunction({
-        ...factoryMeta,
-        delegate: meta.useClass,
-        delegateType: R3FactoryDelegateType.Factory,
-      });
+      result = delegateToFactory(meta.useClass);
     }
   } else if (meta.useFactory !== undefined) {
-    result = compileFactoryFunction({
-      ...factoryMeta,
-      delegate: meta.useFactory,
-      delegateDeps: meta.userDeps || [],
-      delegateType: R3FactoryDelegateType.Function,
-    });
+    if (meta.userDeps !== undefined) {
+      result = compileFactoryFunction({
+        ...factoryMeta,
+        delegate: meta.useFactory,
+        delegateDeps: meta.userDeps || [],
+        delegateType: R3FactoryDelegateType.Function,
+      });
+    } else {
+      result = {
+        statements: [],
+        factory: o.fn([], [new o.ReturnStatement(meta.useFactory.callFn([]))])
+      };
+    }
   } else if (meta.useValue !== undefined) {
     // Note: it's safe to use `meta.useValue` instead of the `USE_VALUE in meta` check used for
     // client code because meta.useValue is an Expression which will be defined even if the actual
@@ -95,7 +96,7 @@ export function compileInjectable(meta: R3InjectableMetadata): InjectableDef {
       expression: o.importExpr(Identifiers.inject).callFn([meta.useExisting]),
     });
   } else {
-    result = compileFactoryFunction(factoryMeta);
+    result = delegateToFactory(meta.type);
   }
 
   const token = meta.type;
@@ -112,3 +113,12 @@ export function compileInjectable(meta: R3InjectableMetadata): InjectableDef {
     statements: result.statements,
   };
 }
+
+function delegateToFactory(type: o.Expression) {
+  return {
+    statements: [],
+    // () => meta.type.ngFactoryDef(t)
+    factory: o.fn([new o.FnParam('t', o.DYNAMIC_TYPE)], [new o.ReturnStatement(type.callMethod(
+                                                            'ngFactoryDef', [o.variable('t')]))])
+  };
+}