Inspector Service tests should not depend on order of widgets coming from Flutter framework

[elliette]

inspector_service_tests are currently failing due to changes to the Flutter framework that affect the order of implementation widgets in the framework. Similar to the changes made in #9321, these tests should be updated to be resilient to framework changes.

[elliette]

Parent issue: #9357

[xuvien]

I hope this issue gets resolved — it’s quite an annoying bug when using DevTools in the latest version of Flutter