Move Chain trait to runtime primitives (#403)

* extract ChainBase to bp-runtime

* post-merge fixes

* cargo fmt --all

* compilation fixes

* reexport BlockNumberOf, HashOf, HeaderOf

bridges/primitives/rialto/src/lib.rs

@@ -20,6 +20,8 @@
 // Runtime-generated DecodeLimit::decode_all_With_depth_limit
 #![allow(clippy::unnecessary_mut_passed)]
 
+use bp_runtime::Chain;
+use frame_support::RuntimeDebug;
 use sp_core::Hasher as HasherT;
 use sp_runtime::traits::BlakeTwo256;
 use sp_std::prelude::*;
@@ -36,6 +38,17 @@ pub type Hasher = BlakeTwo256;
 /// The header type used by Rialto.
 pub type Header = sp_runtime::generic::Header<BlockNumber, Hasher>;
 
+/// Rialto chain.
+#[derive(RuntimeDebug)]
+pub struct Rialto;
+
+impl Chain for Rialto {
+	type BlockNumber = BlockNumber;
+	type Hash = Hash;
+	type Hasher = Hasher;
+	type Header = Header;
+}
+
 sp_api::decl_runtime_apis! {
 	/// API for querying information about Rialto headers from the Bridge Pallet instance.
 	///