- fix regression in create_routes:
fwd_trampoline_onion was not added to the tuple
- fix onion structure for e2e
- maybe_fulfill_htlc:
check the mpp_status of the outer onion,
return trampoline_onion to be forwarded
We pass the private edges to lnrouter, and let it find routes end-to-end.
Previously the edge_cost heuristics didn't apply to the private edges
and we were just randomly picking one of the route hints and use that.
So e.g. cheaper private edges were not preferred, but they are now.
PathEdge now stores both start_node and end_node; not just end_node.
- trampoline node is the final recipient of MPP
- each trampoline receives a bucket of HTLCs
- if a HTLC from a bucket fails, wait for the entire bucket to fail
- move trampoline route and onion code into trampoline module
