Move Onboarding to app-level

[ualch9]

• Onboarding now occurs before the root controller is initialized, replacing Bulletin.
• Moves onboarding responsibility from OBAKit → App (i.e. OneBusAway app).

First-time users can now grant a one-time location authorization for Automatically select region. This permission is independent from a formal location authorization, so it doesn't count against our location permission usage.

Video

(In the video, the recording is dimmed while the location system prompt is presented)

https://user-images.githubusercontent.com/22162410/216621367-4e8fa531-babb-444f-b993-0064cda03b18.mov

[ualch9]

KiedyBus needs the region picker page, but does it need the migration page?

@aaronbrethorst cc @wkulesza

[aaronbrethorst]

This looks great and makes total sense @ualch9, but we'll need to make sure that the WhiteLabel.md and README.markdown files get updated with new instructions to account for these changes.

[ualch9]

Created wiki pages:

• https://github.com/OneBusAway/onebusaway-ios/wiki/Get-Started
• https://github.com/OneBusAway/onebusaway-ios/wiki/White-Label
• https://github.com/OneBusAway/onebusaway-ios/wiki/White-Label-Onboarding

GitHub will host images and has inline Mermaid graph support (nice-looking graphs that are easy to maintain).

[aaronbrethorst]

docs look great, @ualch9. thanks for writing them up

[ualch9]

There is a layering issue because I did not test on a clean script/generate_project, and I originally intended for the OnboardingNavigationController to be placed in OBAKit.framework. This is fixed in #640.