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/platform-webworker/test/web_workers/shared/message_bus_util.ts

@@ -23,7 +23,8 @@ export function createConnectedMessageBus(): MessageBus {
 }
 
 class MockPostMessage {
-  private _listener: EventListener;
+  // TODO(issue/24571): remove '!'.
+  private _listener !: EventListener;
 
   addEventListener(type: string, listener: EventListener, useCapture?: boolean): void {
     if (type === 'message') {