Partial columns cleanup (#9321)

#8314 left a few ugly potentially panicking location behind - all of them believed to be unreachable, but this PR fixes them regardless for good hygiene.


  Update to `ethereum_ssz 0.10.4` for two new helpers: `not_inplace` and `clone_zeroed`.

Remove remaining `expect` and `todo!` in favour of these helpers and one new fallible (but practically infallible) method.


Co-Authored-By: Daniel Knopik <daniel@dknopik.de>

beacon_node/beacon_chain/src/data_column_verification.rs

@@ -1220,7 +1220,16 @@ pub fn validate_partial_data_column_sidecar_for_gossip<T: BeaconChainTypes>(
                 header,
             };
         }
-        Err(MissingCellsError::UnexpectedError(e)) => todo!("handle unexpected error {:?}", e),
+        Err(MissingCellsError::UnexpectedError(e)) => {
+            return PartialColumnVerificationResult::ErrWithValidHeader {
+                err: GossipDataColumnError::InternalError(format!(
+                    "An unexpected error occurred while validating partial data columns: {:?}",
+                    e
+                ))
+                .into(),
+                header,
+            };
+        }
     };
 
     // We do not have to check block related data here, as we create the verifiable column from