Make use of StorageHasher and HasherKind (#2836)

* Make use of StorageHasher and HasherKind.

* Use Storagehasher hasher function for key2 of double map.

* Refactor to reuse hasher from implementation.

* Bump up since there is srml changes.

* Update metadata version.

substrate/node/runtime/src/lib.rs

@@ -59,7 +59,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	impl_name: create_runtime_str!("substrate-node"),
 	authoring_version: 10,
 	spec_version: 92,
-	impl_version: 93,
+	impl_version: 94,
 	apis: RUNTIME_API_VERSIONS,
 };