#PickhardtPayments: fast mode: prune distant edges from graph

[C-Otto]

Is your feature request related to a problem? Please describe.
For any payment between nodes A and B the lightning network might contain channels that are very distant from both A and B. Considering those for the MPP computation seems less beneficial compared to "closer" edges.

Describe the solution you'd like
Add a "fast mode" that prunes such edges from the graph to speed up the computation. This should be optional.

[renepickhardt]

may be relevant: renepickhardt/mpp-splitter#13 I am currently considering to basically multiply the cost of an edge with a number that increases exponentially with the topological distance of the edge from sender and recipient pair before pruning