Fix lightning-block-sync warnings.

Version 0.32.2 of `rust-bitcoin` deprecates a number of methods that
are commonly used in this project, most visibly `txid()`, which is
now called `compute_txid()`. This resulted in a lot of warnings, and
this commit is part of a series that seeks to address that.

Author: arik-so

lightning-block-sync/src/gossip.rs

@@ -198,7 +198,7 @@ where
 						return Err(UtxoLookupError::UnknownTx);
 					}
 
-					outpoint = OutPoint::new(transaction.txid(), output_index.into());
+					outpoint = OutPoint::new(transaction.compute_txid(), output_index.into());
 					output = transaction.output[output_index as usize].clone();
 				}};
 			}

lightning-block-sync/src/poll.rs

@@ -144,8 +144,8 @@ impl ValidatedBlockHeader {
 			if self.height % 2016 == 0 {
 				let target = self.header.target();
 				let previous_target = previous_header.header.target();
-				let min_target = previous_target.min_difficulty_transition_threshold();
-				let max_target = previous_target.max_difficulty_transition_threshold();
+				let min_target = previous_target.min_transition_threshold();
+				let max_target = previous_target.max_transition_threshold_unchecked();
 				if target > max_target || target < min_target {
 					return Err(BlockSourceError::persistent("invalid difficulty transition"));
 				}

lightning-block-sync/src/test_utils.rs

@@ -53,7 +53,7 @@ impl Blockchain {
 				input: vec![],
 				output: vec![],
 			};
-			let merkle_root = TxMerkleNode::from_raw_hash(coinbase.txid().to_raw_hash());
+			let merkle_root = TxMerkleNode::from_raw_hash(coinbase.compute_txid().to_raw_hash());
 			self.blocks.push(Block {
 				header: Header {
 					version: Version::NO_SOFT_FORK_SIGNALLING,