Address review feedback: defer double-SHA256 computations in debug logging

Use a lazy Display wrapper to format confirmed txids, preventing unconditional hashing when DEBUG logging is disabled.

Author: Alkamal01

lightning/src/ln/channelmanager.rs

@@ -15968,8 +15968,14 @@ impl<
 
 		let block_hash = header.block_hash();
 		log_trace!(self.logger, "{} transactions included in block {} at height {} provided", txdata.len(), block_hash, height);
+		struct LazyTxid<'a>(&'a Transaction);
+		impl<'a> core::fmt::Display for LazyTxid<'a> {
+			fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+				write!(f, "{}", self.0.compute_txid())
+			}
+		}
 		for (_, tx) in txdata.iter() {
-			log_debug!(self.logger, "Confirmed transaction {} in block {} at height {}", tx.compute_txid(), block_hash, height);
+			log_debug!(self.logger, "Confirmed transaction {} in block {} at height {}", LazyTxid(tx), block_hash, height);
 		}
 
 		let _persistence_guard =