[NavigationRail] Vertical scrolling support for the Rail

[SupasinTatiyanupanwong]

Is your feature request related to a problem? Please describe.

Our Android app is targeting small tablets and/or embedded Android devices for UAV remote control. We are make use of the Rail as the primary navigation method for the Settings screen due to the screen size contraint.

Right now, we are almost at the limit of the vertical height and the Rail does not support for vertical scrolling. This issue also exist in the Google Photos app when opening on 7-8 inch tablets on landscape orientation.

Describe the solution you'd like

It would be nice if the Rail does support for vertical scrolling thru some kind of flags or by default as if we have more menu items we can displayed vertically.

Describe alternatives you've considered

Swtiching to TabLayout instead is not a good idea based on our UX experiment as it also reduce the screen real estate for the content, so we have switched back to the Rail.

** Additional context **

Googling for the solution to this problem also resulting in similar thing on SO: https://stackoverflow.com/questions/61874835/scrollable-navigation-rail-in-flutter