Add SystemOverlay options to FeedbackThemeData

[Zazo032]

Is your feature request related to a problem? Please describe.
If the AppBar color is light, but the feedback provider background is dart, status bar brightness is not changed so you have dark icons over a dark background.

Describe the solution you'd like
Having a param systemOverlayStyle (just like AppBars) to set the status bar brightness, color... while the feedback provider is open.

Describe alternatives you've considered
Make the show function async so we can await it and programatically change the systemOverlayStyle. Otherwise, a onFeedbackClosed param which gets called when the feedback provider is closed (either manually closed or after submitting the feedback).