Use more points in `get_latest_points`

[SebastienGllmt]

When we launch, we try and find the intersection between Carp and the cardano-node to start syncing. Notably, this is done with the function get_latest_points. Currently, we only use an intersection of a single point, but this could fail if we stop Carp when it's near the tip. We should instead pass in a list of points (such as factors of 2) to avoid getting stuck