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/service/test/src/lib.rs

@@ -139,6 +139,7 @@ fn node_config<F: ServiceFactory> (
 		database_path: root.join("db").to_str().unwrap().into(),
 		database_cache_size: None,
 		state_cache_size: 16777216,
+		state_cache_child_ratio: None,
 		pruning: Default::default(),
 		keys: keys,
 		chain_spec: (*spec).clone(),