feat(ivy): compile @Injectable on classes not meant for DI (#28523)

In the past, @Injectable had no side effects and existing Angular code is
therefore littered with @Injectable usage on classes which are not intended
to be injected.

A common example is:

@Injectable()
class Foo {
  constructor(private notInjectable: string) {}
}

and somewhere else:

providers: [{provide: Foo, useFactory: ...})

Here, there is no need for Foo to be injectable - indeed, it's impossible
for the DI system to create an instance of it, as it has a non-injectable
constructor. The provider configures a factory for the DI system to be
able to create instances of Foo.

Adding @Injectable in Ivy signifies that the class's own constructor, and
not a provider, determines how the class will be created.

This commit adds logic to compile classes which are marked with @Injectable
but are otherwise not injectable, and create an ngInjectableDef field with
a factory function that throws an error. This way, existing code in the wild
continues to compile, but if someone attempts to use the injectable it will
fail with a useful error message.

In the case where strictInjectionParameters is set to true, a compile-time
error is thrown instead of the runtime error, as ngtsc has enough
information to determine when injection couldn't possibly be valid.

PR Close #28523

packages/core/src/di/jit/injectable.ts

@@ -43,7 +43,7 @@ export function compileInjectable(type: Type<any>, srcMeta?: Injectable): void {
           typeArgumentCount: 0,
           providedIn: meta.providedIn,
           ctorDeps: reflectDependencies(type),
-          userDeps: undefined
+          userDeps: undefined,
         };
         if ((isUseClassProvider(meta) || isUseFactoryProvider(meta)) && meta.deps !== undefined) {
           compilerMeta.userDeps = convertDependencies(meta.deps);