test: add DammSum known-answer test (tari-project#6638)

Description
---
Adds a known-answer test for the DammSum checksum implementation.

Motivation and Context
---
The DammSum checksum implementation already had extensive randomized
testing, but did not have any known-answer tests. This PR adds one.

How Has This Been Tested?
---
The new test passes!

What process can a PR reviewer use to test or verify this change?
---
Ensure the test passes. If you're feeling bored, examine the checksum
algorithm to convince yourself of the validity of the test.

Breaking Changes
---

- [x] None
- [ ] Requires data directory on base node to be deleted
- [ ] Requires hard fork
- [ ] Other - Please specify

base_layer/common_types/src/dammsum.rs

@@ -224,4 +224,12 @@ mod test {
             assert_eq!(validate_checksum(&data_), Err(ChecksumError::InvalidChecksum));
         }
     }
+
+    #[test]
+    fn known_checksum() {
+        const SIZE: usize = 33;
+
+        // We know what the checksum for all-zero data must be
+        assert_eq!(compute_checksum(&[0u8; SIZE]), 0u8);
+    }
 }