Refactor `MenuBar` and `StatusBar` to be adornments

[tig]

This is a sub-issue of:

• Master Issue: Finish Adornments  #2994

Todo

• Reimplemen these views based on Bar. See Create a new Bar view to replace StatusBar (and eventually MenuBar) #3073
• Remove the dependency between these classes and Toplevel and enable any view to host a menubar or statusbar (or any View).
• By default Window will have the menubar and statusbar's added to it's Border/Adornment Frame but they will be Visible = false by default. We'll expose helper properties to access them:

win.MenuBar.Visible = true etc...

[tig]

Not entirely sure this is needed.