feat(collator): add seqno to rand seed

collator/src/collator/do_collate.rs

@@ -73,11 +73,15 @@ impl CollatorStdImpl {
             .get_last_imported_anchor_ct_and_author()
             .unwrap();
 
-        // TODO: need to generate unique for each block
-        // generate seed from the chain_time from the anchor
+        // Generate unique rand seed from the anchor chain_time and the next block seqno
         let hash_bytes = sha2::Sha256::digest(next_chain_time.to_be_bytes());
-        let rand_seed = HashBytes::from_slice(hash_bytes.as_slice());
-        tracing::trace!(target: tracing_targets::COLLATOR, "rand_seed from chain time: {}", rand_seed);
+        let seqno = working_state.next_block_id_short.seqno.to_be_bytes();
+        let rand_seed = HashBytes::from_slice(
+            [&hash_bytes.as_slice()[..32 - 4], &seqno[..]]
+                .concat()
+                .as_slice(),
+        );
+        tracing::trace!(target: tracing_targets::COLLATOR, "rand_seed from chain time and block seqno: {}", rand_seed);
 
         let is_masterchain = self.shard_id.is_masterchain();