Track and react to remote partial-claiming of pending claim request

A pending claim request may contain a set of multiple outpoints.
If one or multiple of them get claimed by remote party, our in-flight
claiming transactions aren't valid anymore so we need to react
quickly and regenerate claiming transaction with accurate set.

However, a claimed outpoint may be disconnected and we need to resurrect
back outpoint among set of orignal pending claim request.

To guarantee consistency of contentious claimed outpoint we cache it
as OnchainEvent::ContentionsOutpoint and only delete it after
ANTI_REORG_DELAY.

Fix test broken by change, partial claiming on revoked txn
force us to regenerate txn

Author: Antoine Riard