feat(forms): allow setting submit options at form-level

Updates FormOptions to accept a submission configuration object.
This allows defining default submit options (action, validation behavior, etc.)
when creating the form, which can be overridden when calling submit().

adev/src/content/examples/signal-forms/src/login-validation-complete/app/app.ts

@@ -1,3 +1,11 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
 import {ChangeDetectionStrategy, Component, signal} from '@angular/core';
 import {email, form, FormField, required, submit} from '@angular/forms/signals';
 
@@ -28,11 +36,13 @@ export class App {
 
   onSubmit(event: Event) {
     event.preventDefault();
-    submit(this.loginForm, async () => {
-      const credentials = this.loginModel();
-      // In a real app, this would be async:
-      // await this.authService.login(credentials);
-      console.log('Logging in with:', credentials);
+    submit(this.loginForm, {
+      action: async () => {
+        const credentials = this.loginModel();
+        // In a real app, this would be async:
+        // await this.authService.login(credentials);
+        console.log('Logging in with:', credentials);
+      },
     });
   }
 }