feat: separate waypoint logic

[Archdoog]

• Separates waypoint advance logic out of step advance fn. This reduces the conditional burden required to advance a waypoint. It also enables flexible waypoint advance logic.

[ianthetechie]

Suggested change

	// Condition to advance the remaining waypoints.
	/// Controls when a waypoint should be marked as complete.
	///
	/// While a route may consist of thousands of points, waypoints are special.
	/// A simple trip will have only one waypoint: the final destination.
	/// A more complex trip may have several intermediate stops.
	/// Just as the navigation state keeps track of which steps remain in the route,
	/// it also tracks which waypoints are still remaining.
	///
	/// Tracking waypoints enables Ferrostar to reroute users when they stray off the route line.
	/// The waypoint advance mode specifies how the framework decides
	/// that a waypoint has been visited (and is removed from the list).
	///
	/// NOTE: Advancing to the next *step* and advancing to the next *waypoint*
	/// are separate processes.
	/// This will not normally cause any issues, but keep in mind that
	/// manually advancing to the next step does not *necessarily* imply
	/// that the waypoint will be marked as complete!

[ianthetechie]

Suggested change

	// Trim the remaining waypoints if we should advance.
	// Trim the remaining waypoints if needed.

[ianthetechie]

Nice work! I think you can make this even more compact with the is_some_and like this:

remaining_waypoints.first().is_some_and(|waypoint| {
    // Rest of the inner code
}

Then you can drop the whole if/else wrapper and it's a single expression inside :)