Fulu update to spec v1.6.0-alpha.4 (#7890)

Fulu update to spec [v1.6.0-alpha.4](https://github.com/ethereum/consensus-specs/releases/tag/v1.6.0-alpha.4).
- Make `number_of_columns` a preset
- Optimise `get_custody_groups` to avoid computing if cgc = 128
- Add support for additional typenum values in type_dispatch macro

beacon_node/network/src/sync/network_context.rs

@@ -948,9 +948,10 @@ impl<T: BeaconChainTypes> SyncNetworkContext<T> {
         self.send_network_msg(NetworkMessage::SendRequest {
             peer_id,
             request: RequestType::DataColumnsByRoot(
-                request
-                    .clone()
-                    .try_into_request(self.fork_context.current_fork_name(), &self.chain.spec)?,
+                request.clone().try_into_request::<T::EthSpec>(
+                    self.fork_context.current_fork_name(),
+                    &self.chain.spec,
+                )?,
             ),
             app_request_id: AppRequestId::Sync(SyncRequestId::DataColumnsByRoot(id)),
         })?;