perf(forms): use ngDevMode to tree-shake _ngModelWarning (#39964)

This commit adds `ngDevMode` guard to call `_ngModelWarning` only
in dev mode (similar to how things work in other parts of Ivy runtime code).
The `ngDevMode` flag helps to tree-shake this function from production builds
(since it will act as no-op, in dev mode everything will work as it works right now)
to decrease production bundle size.

PR Close #39964

packages/forms/src/directives/reactive_directives/form_control_directive.ts

@@ -125,7 +125,9 @@ export class FormControlDirective extends NgControl implements OnChanges {
       this.form.updateValueAndValidity({emitEvent: false});
     }
     if (isPropertyUpdated(changes, this.viewModel)) {
-      _ngModelWarning('formControl', FormControlDirective, this, this._ngModelWarningConfig);
+      if (typeof ngDevMode === 'undefined' || ngDevMode) {
+        _ngModelWarning('formControl', FormControlDirective, this, this._ngModelWarningConfig);
+      }
       this.form.setValue(this.model);
       this.viewModel = this.model;
     }

packages/forms/src/directives/reactive_directives/form_control_name.ts

@@ -145,7 +145,9 @@ export class FormControlName extends NgControl implements OnChanges, OnDestroy {
   ngOnChanges(changes: SimpleChanges) {
     if (!this._added) this._setUpControl();
     if (isPropertyUpdated(changes, this.viewModel)) {
-      _ngModelWarning('formControlName', FormControlName, this, this._ngModelWarningConfig);
+      if (typeof ngDevMode === 'undefined' || ngDevMode) {
+        _ngModelWarning('formControlName', FormControlName, this, this._ngModelWarningConfig);
+      }
       this.viewModel = this.model;
       this.formDirective.updateModel(this, this.model);
     }

packages/forms/src/directives/shared.ts

@@ -6,8 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {isDevMode} from '@angular/core';
-
 import {AbstractControl, FormArray, FormControl, FormGroup} from '../model';
 import {getControlAsyncValidators, getControlValidators, mergeValidators} from '../validators';
 
@@ -324,13 +322,11 @@ export function removeListItem<T>(list: T[], el: T): void {
 export function _ngModelWarning(
     name: string, type: {_ngModelWarningSentOnce: boolean},
     instance: {_ngModelWarningSent: boolean}, warningConfig: string|null) {
-  if (!isDevMode() || warningConfig === 'never') return;
+  if (warningConfig === 'never') return;
 
   if (((warningConfig === null || warningConfig === 'once') && !type._ngModelWarningSentOnce) ||
       (warningConfig === 'always' && !instance._ngModelWarningSent)) {
-    if (typeof ngDevMode === 'undefined' || ngDevMode) {
-      ReactiveErrors.ngModelWarning(name);
-    }
+    ReactiveErrors.ngModelWarning(name);
     type._ngModelWarningSentOnce = true;
     instance._ngModelWarningSent = true;
   }