Enforce max_block_size

Omit transactions that exceed max_block_size from payload. Use mocked
`max_block_size` for now.

sequencer/src/block/payload.rs

@@ -160,7 +160,13 @@ impl<TableWord: TableWordTraits> Payload<TableWord> {
             raw_payload: vec![],
             ns_table: NameSpaceTable::default(),
         };
+        let mut block_size = 0u64;
         for tx in txs.into_iter() {
+            block_size += tx.payload().len() as u64;
+            // TODO max_block_size will be passed in
+            if block_size >= crate::ChainConfig::default().max_block_size() {
+                break;
+            }
             Payload::<TableWord>::update_namespace_with_tx(&mut namespaces, tx);
         }