At the moment, for our or their unilateral close, we create a resolved[]
entry for our output, their output, and each HTLC, in cstate order. Some
of these outputs might not exist (too small), so it's actually better
to simply keep a resolved[] entry for each of the tx's actual outputs.
(We already changed the steal resolved[] array to work like this, but
these are trickier, since we rely on that order if we need to fulfill an
on-chain HTLC).
It also helps as we are weaning off knowing the cstate and permutation
mapping for each commitment transaction.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>