Provide a mechanism to better simulate safe areas in a golden test

[coreysprague]

A common class of visual UI bugs is content extending incorrectly into the safe area. The top notch is the easiest example to think of, but the bottom safe area is equally important on an iPhone X/XS, etc.

It should be easy enough to expose viewInsets into the Device configuration. However, we should consider applying an overlay onto the widget under test to highlight the safe areas.

[coreysprague]

Note, the work to allow for configuration of the safe areas was completed here: https://github.com/eBay/flutter_glove_box/pull/33

Leaving this issue open though because I think we should consider a visual overlay to indicate where the unsafe area is