perf(ivy): remove check for function type in renderStringify (#30838)

The `renderStringify` function shows up pretty high in the CPU profiling.
Turns out that this function contained unnecessary `typeof` check for
function types - the check only makes sense / is used in error messages.

The PR also alligns how ivy and view engine stringify functions used in
interpolations.

PR Close #30838

packages/core/test/acceptance/text_spec.ts

@@ -112,4 +112,20 @@ describe('text instructions', () => {
 
     expect(div.innerHTML).toBe('<h1>LOL, big text</h1>');
   });
+
+  it('should stringify functions used in bindings', () => {
+    @Component({
+      template: '<div>{{test}}</div>',
+    })
+    class App {
+      test = function foo() {};
+    }
+
+    TestBed.configureTestingModule({declarations: [App]});
+    const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
+    const div = fixture.nativeElement.querySelector('div');
+
+    expect(div.innerHTML).toBe('function foo() { }');
+  });
 });