get_checksum_bytes now checks input data for checksum

If `exclude_hash` is set, we split the input data, and if a checksum
already existed within the original data, we check the calculated
checksum against the original checksum.

Additionally, the implementation of `IntoWalletDescriptor` for `&str`
has been refactored for clarity.

src/wallet/mod.rs

@@ -1943,15 +1943,10 @@ pub(crate) mod test {
         let (wallet, _, _) = get_funded_wallet(get_test_wpkh());
         let checksum = wallet.descriptor_checksum(KeychainKind::External);
         assert_eq!(checksum.len(), 8);
-
-        let raw_descriptor = wallet
-            .descriptor
-            .to_string()
-            .split_once('#')
-            .unwrap()
-            .0
-            .to_string();
-        assert_eq!(get_checksum(&raw_descriptor).unwrap(), checksum);
+        assert_eq!(
+            get_checksum(&wallet.descriptor.to_string()).unwrap(),
+            checksum
+        );
     }
 
     #[test]