Add missing child trie rpc on_custom_message handler (#3522)

* missing on_custom for child read.

* fix and complete, add test cases.

* shorten line.

* replace vecs of key value tuple with maps.

substrate/core/test-runtime/src/genesismap.rs

@@ -30,7 +30,8 @@ pub struct GenesisConfig {
 	balances: Vec<(AccountId, u64)>,
 	heap_pages_override: Option<u64>,
 	/// Additional storage key pairs that will be added to the genesis map.
-	extra_storage: Vec<(Vec<u8>, Vec<u8>)>,
+	extra_storage: HashMap<Vec<u8>, Vec<u8>>,
+	child_extra_storage: HashMap<Vec<u8>, HashMap<Vec<u8>, Vec<u8>>>,
 }
 
 impl GenesisConfig {
@@ -40,7 +41,8 @@ impl GenesisConfig {
 		endowed_accounts: Vec<AccountId>,
 		balance: u64,
 		heap_pages_override: Option<u64>,
-		extra_storage: Vec<(Vec<u8>, Vec<u8>)>,
+		extra_storage: HashMap<Vec<u8>, Vec<u8>>,
+		child_extra_storage: HashMap<Vec<u8>, HashMap<Vec<u8>, Vec<u8>>>,
 	) -> Self {
 		GenesisConfig {
 			changes_trie_config: match support_changes_trie {
@@ -51,6 +53,7 @@ impl GenesisConfig {
 			balances: endowed_accounts.into_iter().map(|a| (a, balance)).collect(),
 			heap_pages_override,
 			extra_storage,
+			child_extra_storage,
 		}
 	}
 
@@ -75,10 +78,9 @@ impl GenesisConfig {
 		}
 		map.insert(twox_128(&b"sys:auth"[..])[..].to_vec(), self.authorities.encode());
 		// Finally, add the extra storage entries.
-		for (key, value) in self.extra_storage.iter().cloned() {
-			map.insert(key, value);
-		}
-		(map, Default::default())
+		map.extend(self.extra_storage.clone().into_iter());
+
+		(map, self.child_extra_storage.clone())
 	}
 }