fix(language-service): Turn on strict mode for test project (#32783)

This is the last part in refactoring of the test project.
This PR turns on strict mode for typechecking and fixed tests that
fail under this mode.

PR Close #32783

packages/language-service/test/project/app/ng-for-cases.ts

@@ -29,7 +29,7 @@ export class UnknownPeople {
     </div>`,
 })
 export class UnknownEven {
-  people: Person[];
+  people: Person[] = [];
 }
 
 @Component({
@@ -39,5 +39,5 @@ export class UnknownEven {
     </div>`,
 })
 export class UnknownTrackBy {
-  people: Person[];
+  people: Person[] = [];
 }