move signed extension stuff from prolkadot-core primitives to bridge-hub-cumulus-primitives (#1968)

bridges/primitives/chain-rialto-parachain/Cargo.toml

@@ -10,6 +10,7 @@ license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 
 # Bridge Dependencies
 
+bp-bridge-hub-cumulus = { path = "../chain-bridge-hub-cumulus", default-features = false }
 bp-messages = { path = "../messages", default-features = false }
 bp-polkadot-core = { path = "../polkadot-core", default-features = false }
 bp-runtime = { path = "../runtime", default-features = false }
@@ -26,6 +27,7 @@ sp-std = { git = "https://github.com/paritytech/substrate", branch = "master", d
 [features]
 default = ["std"]
 std = [
+	"bp-bridge-hub-cumulus/std",
 	"bp-messages/std",
 	"bp-runtime/std",
 	"frame-support/std",

bridges/primitives/chain-rialto-parachain/src/lib.rs

@@ -133,7 +133,9 @@ impl Parachain for RialtoParachain {
 	const PARACHAIN_ID: u32 = RIALTO_PARACHAIN_ID;
 }
 
-pub use bp_polkadot_core::DefaultSignedExtension as SignedExtension;
+// Technically this is incorrect, because rialto-parachain isn't a bridge hub, but we're
+// trying to keep it close to the bridge hubs code (at least in this aspect).
+pub use bp_bridge_hub_cumulus::SignedExtension;
 
 frame_support::parameter_types! {
 	pub BlockLength: limits::BlockLength =