Manual node +channel prioritization

[TheBlueMatt]

We should have a method in our scorer to manually peanalize (or negative penalty) a given node or channel. Would be cool to have it not decay, too.

[tnull]

Is this still of interest? Do we rather want this to be on a per-node or a per-channel basis? If it's the former I guess it would be a really easy generalization of #1550, i.e., instead of storing banned nodes in a HashSet we'd store manual penalties in a HashMap and banning nodes would simply be adding u64::max_value() penalties.

[jkczyz]

Not sure what the context was for this issue. Looks like it predated ProbabilisticScorer or at least was filed while at an earlier stage of the review.

[TheBlueMatt]

Hmm, yea, I mean I guess #1550 mostly did this, but indeed, I guess it'd be nice to generalize it. Its certainly not critical now that we have a banned nodes list, though.