Swap `Vec<&RouteHop>` parameters for slices

Swap `Vec<&RouteHop>` parameters for slices

In c353c3ed7c40e689a3b9fb6730c6dabbd3c92cc5, new scorer-updating
methods were added to the `Router` object, however they were
passed as a `Vec` of references. We use the list-of-references
pattern to make bindings simpler (by not requiring allocations per
entry), however there's no reason prefer to passing a `Vec` over
a slice, given the `Vec` doesn't hold ownership of the objects
anyway.