add last_id to Entry, PohEntry (#1783)

add prev_id to Entry, PohEntry

src/cluster_info.rs

@@ -1670,8 +1670,12 @@ mod tests {
             let zero = Hash::default();
             let one = hash(&zero.as_ref());
             writer
-                .write_entries(&vec![Entry::new_tick(0, &zero), Entry::new_tick(0, &one)].to_vec())
-                .unwrap();
+                .write_entries(
+                    &vec![
+                        Entry::new_tick(&zero, 0, &zero),
+                        Entry::new_tick(&one, 0, &one),
+                    ].to_vec(),
+                ).unwrap();
             path
         }