Use new block requests protocol (#5760)

* Use new block requests protocol

* Tweak comment

substrate/client/network/src/config.rs

@@ -399,7 +399,10 @@ pub struct NetworkConfiguration {
 	/// Maximum number of peers to ask the same blocks in parallel.
 	pub max_parallel_downloads: u32,
 	/// Should we insert non-global addresses into the DHT?
-	pub allow_non_globals_in_dht: bool
+	pub allow_non_globals_in_dht: bool,
+	/// If true, uses the `/<chainid>/block-requests/<version>` experimental protocol rather than
+	/// the legacy substream. This option is meant to be hard-wired to `true` in the future.
+	pub use_new_block_requests_protocol: bool,
 }
 
 impl NetworkConfiguration {
@@ -430,7 +433,8 @@ impl NetworkConfiguration {
 				use_yamux_flow_control: false,
 			},
 			max_parallel_downloads: 5,
-			allow_non_globals_in_dht: false
+			allow_non_globals_in_dht: false,
+			use_new_block_requests_protocol: true,
 		}
 	}
 }