Flutter inspector for widget tests

[xster]

Debugging complex widget tests often involves a lot of debugDumpApp() to look at the current state of the UI but terminal tree dumps are unwieldy. Especially trying to connect widgets with render objects. Would be awesome to bring the power of the inspector to tests.

[devoncarew]

cc @jacob314 for FYI

[ivan-horchakov]

I'm totally agreed. For example, Xamarin (C#) has an awesome app.Repl() which prints out in the terminal compact & understandable tree without all unnecessary info like debugDumpApp().

[rollin-s]

Absolutely. It would be so useful.