Refactor, update, and move around testing/scenario_app/README.md (flutter/engine#50659)
I'm not sure about long-term direction re: separating the Android and
iOS code, but other than `lib/*.dart`, all of the code in
`testing/scenario_app/**` is platform-specific. Therefore, I've moved
the documentation around, and added to it where it made sense, in order
to make it easier for someone else to grok.
Index:
-
[`testing/scenario_app/README.md`](5012e1fd5d/testing/scenario_app/README.md)
-
[`testing/scenario_app/bin/README.md`](5012e1fd5d/testing/scenario_app/bin/README.md)
-
[`testing/scenario_app/android/README.md`](5012e1fd5d/testing/scenario_app/android/README.md)
-
[`testing/scenario_app/ios/README.md`](5012e1fd5d/testing/scenario_app/ios/README.md)
This also gives me an obvious place to further document how the Android
tests work:
<a
href="5012e1fd5d/testing/scenario_app/android/README.md"><img
width="880" alt="Screenshot 2024-02-14 at 12 35 39 PM"
src="https://github.com/flutter/engine/assets/168174/d4663005-d770-4003-a3fa-74ae8bf635c4"></a>
Closes https://github.com/flutter/flutter/issues/143350.
---------
Co-authored-by: Jenn Magder <magder@google.com>
Co-authored-by: Gray Mackall <34871572+gmackall@users.noreply.github.com>