Set StateBackend::Transaction to PrefixedMemoryDB (#14612)

* Yep

* Try to get it working everywhere

* Make `from_raw_storage` start with an empty db

* More fixes!

* Make everything compile

* Fix `child_storage_root`

* Fix after merge

* Cleanups

* Update primitives/state-machine/src/overlayed_changes/mod.rs

Co-authored-by: Davide Galassi <davxy@datawok.net>

* Review comments

* Fix issues

* Silence warning

* FMT

* Clippy

---------

Co-authored-by: Davide Galassi <davxy@datawok.net>

substrate/client/api/src/call_executor.rs

@@ -26,7 +26,7 @@ use sp_state_machine::{OverlayedChanges, StorageProof};
 use std::cell::RefCell;
 
 use crate::execution_extensions::ExecutionExtensions;
-use sp_api::{ProofRecorder, StorageTransactionCache};
+use sp_api::{HashingFor, ProofRecorder};
 
 /// Executor Provider
 pub trait ExecutorProvider<Block: BlockT> {
@@ -72,12 +72,7 @@ pub trait CallExecutor<B: BlockT>: RuntimeVersionOf {
 		at_hash: B::Hash,
 		method: &str,
 		call_data: &[u8],
-		changes: &RefCell<OverlayedChanges>,
-		storage_transaction_cache: Option<
-			&RefCell<
-				StorageTransactionCache<B, <Self::Backend as crate::backend::Backend<B>>::State>,
-			>,
-		>,
+		changes: &RefCell<OverlayedChanges<HashingFor<B>>>,
 		proof_recorder: &Option<ProofRecorder<B>>,
 		call_context: CallContext,
 		extensions: &RefCell<Extensions>,