ln: handle trampoline claims on restart

This commit uses the existing outbound payment claims replay logic
to restore trampoline claims. If any single previous hop in a htlc
source with multiple previous hops requires claim, we represent this
with a single outbound claimed htlc because we assume that *all* of
the incoming htlcs are represented in the source, and will be
appropriately claimed (rather than submitting multiple claims, which
will end up being duplicates of each other). This is the case for
trampoline payments, where the htlc_source stores all previous hops.

Author: carlaKC

lightning/src/ln/channelmanager.rs

@@ -18462,6 +18462,9 @@ where
 
 						let prev_htlcs = match &htlc_source {
 							HTLCSource::PreviousHopData(prev_hop) => vec![prev_hop],
+							HTLCSource::TrampolineForward { previous_hop_data, .. } => {
+								previous_hop_data.iter().collect()
+							},
 							// If it was an outbound payment, we've handled it above - if a preimage
 							// came in and we persisted the `ChannelManager` we either handled it
 							// and are good to go or the channel force-closed - we don't have to
@@ -18495,6 +18498,10 @@ where
 
 								fail_read |= fail_claim_read;
 								return Some((
+									// When we have multiple prev_htlcs we assume that they all
+									// share the same htlc_source which contains all previous hops,
+									// so we can exit on the first claimable prev_hop because this
+									// will result in all prev_hops being claimed.
 									htlc_source,
 									payment_preimage,
 									htlc.amount_msat,