refactor(forms): remove ngForm element selector (#33058)

Removes the deprecated `ngForm` element selector and all of the code related to it.

BREAKING CHANGES:
* `<ngForm></ngForm>` can no longer be used as a selector. Use `<ng-form></ng-form>` instead.
* The `NgFromSelectorWarning` directive has been removed.
* `FormsModule.withConfig` has been removed. Use the `FormsModule` directly.

PR Close #33058

packages/forms/src/directives/ng_form.ts

@@ -94,7 +94,7 @@ const resolvedPromise = (() => Promise.resolve(null))();
  * @publicApi
  */
 @Directive({
-  selector: 'form:not([ngNoForm]):not([formGroup]),ngForm,ng-form,[ngForm]',
+  selector: 'form:not([ngNoForm]):not([formGroup]),ng-form,[ngForm]',
   providers: [formDirectiveProvider],
   host: {'(submit)': 'onSubmit($event)', '(reset)': 'onReset()'},
   outputs: ['ngSubmit'],