Allow starting a saved plan from a specific point

I’d like the ability to start a saved plan from a specific point in the route rather than always starting from the beginning.

A use case for this is when multiple drivers are sharing the same vehicle and have separate Android Auto profiles during the same journey. For example, the saved plan might be:

A (Home) → B (Driver change) → C (Destination)

When the drivers swap at B, the second driver should be able to select the saved plan and choose:

Start plan from: B

If if the selected start point is ambiguous (e.g. in the case of a round rip plan the driver should be prompted on how to resume):

Continue towards: A

Continue towards: C

ABPR would then treat B as the current starting point and navigate through the remaining part of the saved plan, rather than trying to navigate from A to B first.

This would also be useful for other situations where someone joins, resumes, or takes over a journey part-way through, without requiring them to create a new plan or modify the original saved plan.

Ideally, the user could select any point/stop in the saved plan as the starting point and ABPR would continue from there using the existing route and remaining destinations.