FR - LayoutExplorer - Add option to quick jump to overflowing widget

Having an option to quick jump to the widget causing the render overflow error would make it easier for users to diagnose layout issues and would avoid mistakes where users are inspecting the incorrect widget. See https://github.com/flutter/devtools/issues/1545

If there are multiple widgets causing errors, perhaps we could populate a dropdown with the current error-causing widgets.

Read the linked issue #1545 first, then locate LayoutExplorer and the render-overflow error handling entry point in the DevTools repository. Confirm how offending widgets are identified; done means a quick-jump control selects each reported widget, with a dropdown when multiple widgets are reported.

Written by the indexing model from the issue text.