Add UIA Verification of Successful New App Launch to Init Tests

[NickGerleman]

We have runtime tests against several flavors in prebuilt projects, but do not do runtime validation that a newly created template app works successfully. We instead currently just test publish, build, and deploy.

facebook/react-native#31652 adds a distinct testID to the new app screen so that we can validate via UIA that a new application has launched successfully. Our UIA testing tooling is now decoupled from E2ETest, which should make it pretty easy to extend existing init tests to add the runtime validation.

[asklar]

Should try to get this into 0.66