Change inspector expansion strategy

[kenzieschmoll]

Instead of expanding the entire inspector summary tree by default, we should switch to expanding only to the selected widget. This means that only nodes on the direct path to the selected widget would be expanded. This would help to limit the case where we have lots of whitespace and guidelines that make the tree hard to navigate:

This pattern is consistent with some internal android tooling does.

[jacob314]

This seems like a good thing to prioritize. This can be solved purely on the client side in DevTools.