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/language-service/test/test_utils.ts

@@ -65,7 +65,8 @@ missingCache.set('/node_modules/@angular/forms/src/directives/form_interface.met
 
 export class MockTypescriptHost implements ts.LanguageServiceHost {
   private angularPath: string|undefined;
-  private nodeModulesPath: string;
+  // TODO(issue/24571): remove '!'.
+  private nodeModulesPath !: string;
   private scriptVersion = new Map<string, number>();
   private overrides = new Map<string, string>();
   private projectVersion = 0;