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/compiler/testing/src/resource_loader_mock.ts

@@ -99,8 +99,10 @@ export class MockResourceLoader extends ResourceLoader {
 }
 
 class _PendingRequest {
-  resolve: (result: string) => void;
-  reject: (error: any) => void;
+  // TODO(issue/24571): remove '!'.
+  resolve !: (result: string) => void;
+  // TODO(issue/24571): remove '!'.
+  reject !: (error: any) => void;
   promise: Promise<string>;
 
   constructor(public url: string) {