build(bazel): Turning on strictPropertyInitialization for Angular. (#24572)

All errors for existing fields have been detected and suppressed with a
`!` assertion.

Issue/24571 is tracking proper clean up of those instances.

One-line change required in ivy/compilation.ts, because it appears that
the new syntax causes tsickle emitted node to no longer track their
original sourceFiles.

PR Close #24572

packages/forms/src/model.ts

@@ -133,18 +133,22 @@ function isOptionsObj(
  */
 export abstract class AbstractControl {
   /** @internal */
-  _pendingDirty: boolean;
+  // TODO(issue/24571): remove '!'.
+  _pendingDirty !: boolean;
 
   /** @internal */
-  _pendingTouched: boolean;
+  // TODO(issue/24571): remove '!'.
+  _pendingTouched !: boolean;
 
   /** @internal */
   _onCollectionChange = () => {};
 
   /** @internal */
-  _updateOn: FormHooks;
+  // TODO(issue/24571): remove '!'.
+  _updateOn !: FormHooks;
 
-  private _parent: FormGroup|FormArray;
+  // TODO(issue/24571): remove '!'.
+  private _parent !: FormGroup | FormArray;
   private _asyncValidationSubscription: any;
 
   /**
@@ -184,7 +188,8 @@ export abstract class AbstractControl {
    * These status values are mutually exclusive, so a control cannot be
    * both valid AND invalid or invalid AND disabled.
    */
-  public readonly status: string;
+  // TODO(issue/24571): remove '!'.
+  public readonly status !: string;
 
   /**
    * A control is `valid` when its `status` is `VALID`.
@@ -244,7 +249,8 @@ export abstract class AbstractControl {
    * An object containing any errors generated by failing validation,
    * or null if there are no errors.
    */
-  public readonly errors: ValidationErrors|null;
+  // TODO(issue/24571): remove '!'.
+  public readonly errors !: ValidationErrors | null;
 
   /**
    * A control is `pristine` if the user has not yet changed
@@ -284,13 +290,15 @@ export abstract class AbstractControl {
    * A multicasting observable that emits an event every time the value of the control changes, in
    * the UI or programmatically.
    */
-  public readonly valueChanges: Observable<any>;
+  // TODO(issue/24571): remove '!'.
+  public readonly valueChanges !: Observable<any>;
 
   /**
    * A multicasting observable that emits an event every time the validation `status` of the control
    * recalculates.
    */
-  public readonly statusChanges: Observable<any>;
+  // TODO(issue/24571): remove '!'.
+  public readonly statusChanges !: Observable<any>;
 
   /**
    * Reports the update strategy of the `AbstractControl` (meaning