Summary:
The RN OSS release process includes manual testing that a new template app can be started under various platforms, JS engines, etc. This should ideally be automated, to help reduce wasted engineer-time, and to allow reliably increasing release velocity.
`react-native-windows` does already have tests to create and build template projects across our matrix, but they do not do any runtime validation on the newly created app. Adding a `testID` to the new app screen header gives us something to search for in black-box testing to validate that the app started successfully. This should help catch cases where a sample project in repo has changes not reflected in a newly created template app.
## Changelog
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[Internal] [Added] - Add testID to NewAppScreen Header Component
Pull Request resolved: https://github.com/facebook/react-native/pull/31652
Test Plan: Did not manually validate the change, though did check that `ImageBackground` forwards props to `Image`, and that `Image` is aware of `testID` and will forward to the native component.
Reviewed By: kacieb
Differential Revision: D28907197
Pulled By: p-sun
fbshipit-source-id: db3974294afba25878383f1955cad37b69d95da3
Nick Gerleman
41f145fa47