Fix key collision for child trie (#4162)

* In progress, runtime io must switch to future proof root +
child_specific (unique id) + u32 type.

* Switch interface, sr-io seems ok, rpc could use similar interface to
sr-io, genesis json broken if there is child trie in existing encoding
genesis.

* test from previous implementation.

* fix proving test.

* Restore Keyspacedb from other branch, only apply to child trie.

* Removing unneeded child_info from child root (child info are stored
if things changed, otherwhise the root does not change).

* Switch rpc to use same format as ext: more future proof.

* use root from child info for trie backend essence.

* Breaking long lines.

* Update doc and clean pr a bit.

* fix error type

* Restore removed doc on merge and update sr-io doc.

* Switch child storage api to use directly unique id, if managed id
where to be put in place, the api will change at this time.

* Clean deprecated host interface from child.

* Removing assertion on child info (can fail depending on root
memoization).

* merging child info in the overlay when possible.

* child iteration by prefix using child_info.

* Using ChainInfo in frame support. ChainInfo gets redesign to avoid
buffers allocation on every calls.

* Add length of root to the data of child info.

* comments

* Encode compact.

* Remove child info with root.

* Fix try_update condition.

* Comment Ext child root caching.

* Replace tuples by struct with field

* remove StorageTuple alias.

* Fix doc tests, and remove StorageOverlay and ChildStorageOverlay
aliases.

substrate/client/src/light/fetcher.rs

@@ -339,11 +339,13 @@ pub mod tests {
 	use crate::light::fetcher::{FetchChecker, LightDataChecker, RemoteHeaderRequest};
 	use crate::light::blockchain::tests::{DummyStorage, DummyBlockchain};
 	use primitives::{blake2_256, Blake2Hasher, H256};
-	use primitives::storage::{well_known_keys, StorageKey};
+	use primitives::storage::{well_known_keys, StorageKey, ChildInfo};
 	use sp_runtime::generic::BlockId;
 	use state_machine::Backend;
 	use super::*;
 
+	const CHILD_INFO_1: ChildInfo<'static> = ChildInfo::new_default(b"unique_id_1");
+
 	type TestChecker = LightDataChecker<
 		NativeExecutor<test_client::LocalExecutor>,
 		Blake2Hasher,
@@ -394,8 +396,12 @@ pub mod tests {
 		use test_client::TestClientBuilderExt;
 		// prepare remote client
 		let remote_client = test_client::TestClientBuilder::new()
-			.add_extra_child_storage(b":child_storage:default:child1".to_vec(), b"key1".to_vec(), b"value1".to_vec())
-			.build();
+			.add_extra_child_storage(
+				b":child_storage:default:child1".to_vec(),
+				CHILD_INFO_1,
+				b"key1".to_vec(),
+				b"value1".to_vec(),
+			).build();
 		let remote_block_id = BlockId::Number(0);
 		let remote_block_hash = remote_client.block_hash(0).unwrap().unwrap();
 		let mut remote_block_header = remote_client.header(&remote_block_id).unwrap().unwrap();
@@ -406,12 +412,14 @@ pub mod tests {
 		let child_value = remote_client.child_storage(
 			&remote_block_id,
 			&StorageKey(b":child_storage:default:child1".to_vec()),
+			CHILD_INFO_1,
 			&StorageKey(b"key1".to_vec()),
 		).unwrap().unwrap().0;
 		assert_eq!(b"value1"[..], child_value[..]);
 		let remote_read_proof = remote_client.read_child_proof(
 			&remote_block_id,
 			b":child_storage:default:child1",
+			CHILD_INFO_1,
 			&[b"key1"],
 		).unwrap();
 
@@ -487,11 +495,14 @@ pub mod tests {
 			remote_read_proof,
 			result,
 		) = prepare_for_read_child_proof_check();
+		let child_infos = CHILD_INFO_1.info();
 		assert_eq!((&local_checker as &dyn FetchChecker<Block>).check_read_child_proof(
 			&RemoteReadChildRequest::<Header> {
 				block: remote_block_header.hash(),
 				header: remote_block_header,
 				storage_key: b":child_storage:default:child1".to_vec(),
+				child_info: child_infos.0.to_vec(),
+				child_type: child_infos.1,
 				keys: vec![b"key1".to_vec()],
 				retry_count: None,
 			},