Add storage cache for child trie and notification internals (#2639)

* child cache, and test failing notifications

* fix tests and no listen child on top wildcard

* remove useless method

* bump impl version

* Update core/client/src/notifications.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Update core/client/src/notifications.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Update core/client/src/notifications.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Update core/client/src/notifications.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* factoring notification methods to remove some redundant code.

* test child sub removal

* HStorage implementation and some type alias.

* Remove HStorage cache: does not fit

* fix removal

* Make cache use byte length (shared) instead of number of kv

* Make use of hashes cache in rpc

* applying ratio on different lru caches

* Fix format

* break a line

* Remove per element overhead of lru cache.

* typo

substrate/core/state-machine/src/backend.rs

@@ -51,6 +51,11 @@ pub trait Backend<H: Hasher> {
 	/// Get keyed child storage or None if there is nothing associated.
 	fn child_storage(&self, storage_key: &[u8], key: &[u8]) -> Result<Option<Vec<u8>>, Self::Error>;
 
+	/// Get child keyed storage value hash or None if there is nothing associated.
+	fn child_storage_hash(&self, storage_key: &[u8], key: &[u8]) -> Result<Option<H::Out>, Self::Error> {
+		self.child_storage(storage_key, key).map(|v| v.map(|v| H::hash(&v)))
+	}
+
 	/// true if a key exists in storage.
 	fn exists_storage(&self, key: &[u8]) -> Result<bool, Self::Error> {
 		Ok(self.storage(key)?.is_some())

substrate/core/state-machine/src/overlayed_changes.rs

@@ -255,9 +255,13 @@ impl OverlayedChanges {
 	///
 	/// Panics:
 	/// Will panic if there are any uncommitted prospective changes.
-	pub fn into_committed(self) -> impl Iterator<Item=(Vec<u8>, Option<Vec<u8>>)> {
+	pub fn into_committed(self) -> (
+		impl Iterator<Item=(Vec<u8>, Option<Vec<u8>>)>,
+		impl Iterator<Item=(Vec<u8>, impl Iterator<Item=(Vec<u8>, Option<Vec<u8>>)>)>,
+	){
 		assert!(self.prospective.is_empty());
-		self.committed.top.into_iter().map(|(k, v)| (k, v.value))
+		(self.committed.top.into_iter().map(|(k, v)| (k, v.value)),
+			self.committed.children.into_iter().map(|(sk, v)| (sk, v.1.into_iter())))
 	}
 
 	/// Inserts storage entry responsible for current extrinsic index.