[bdk_chain_redesign] Fix calculation bugs.

* `IndexedTxGraph::try_balance` should include "confirmed and spendable"
  into `confirmed` balance.
* `TxGraph::try_list_chain_unspents` filter logic should be reversed.

crates/chain/src/tx_graph.rs

@@ -860,7 +860,7 @@ impl<A: Anchor> TxGraph<A> {
         chain_tip: BlockId,
     ) -> impl Iterator<Item = Result<FullTxOut<ObservedAs<A>>, C::Error>> + 'a {
         self.try_list_chain_txouts(chain, chain_tip)
-            .filter(|r| !matches!(r, Ok(txo) if txo.spent_by.is_none()))
+            .filter(|r| matches!(r, Ok(txo) if txo.spent_by.is_none()))
     }
 
     /// List unspent outputs (UTXOs) that are in `chain` with `chain_tip`.