Split get_tx into its own trait

to make supporting verify_tx easier

src/blockchain/esplora/ureq.rs

@@ -87,10 +87,6 @@ impl Blockchain for EsploraBlockchain {
         .collect()
     }
 
-    fn get_tx(&self, txid: &Txid) -> Result<Option<Transaction>, Error> {
-        Ok(self.url_client._get_tx(txid)?)
-    }
-
     fn broadcast(&self, tx: &Transaction) -> Result<(), Error> {
         let _txid = self.url_client._broadcast(tx)?;
         Ok(())
@@ -108,6 +104,12 @@ impl GetHeight for EsploraBlockchain {
     }
 }
 
+impl GetTx for EsploraBlockchain {
+    fn get_tx(&self, txid: &Txid) -> Result<Option<Transaction>, Error> {
+        Ok(self.url_client._get_tx(txid)?)
+    }
+}
+
 impl WalletSync for EsploraBlockchain {
     fn wallet_setup<D: BatchDatabase>(
         &self,