[iOS] Ability to select location provider and waypoints in demo app

Context from initial discussion:

Yeah, my thought was use the settings page to easily configure this as well as waypoints. Thinking:

1. Tap the gear,
2. Switch for LocationProviding (Simulated, Live)
3. Any permission requirements.
4. Editable list of waypoints (we can absolutely also enable the tap map to add them).

This stuff can all easily be done with some SwiftUI and the @AppStorage decorator.

I agree though, that should be its own ticket after this is merged.

_Originally posted by @Archdoog in https://github.com/stadiamaps/ferrostar/pull/34#discussion_r1452626938_