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/bin/node/cli/benches/block_production.rs

@@ -112,13 +112,7 @@ fn extrinsic_set_time(now: u64) -> OpaqueExtrinsic {
 	.into()
 }
 
-fn import_block(
-	mut client: &FullClient,
-	built: BuiltBlock<
-		node_primitives::Block,
-		<FullClient as sp_api::CallApiAt<node_primitives::Block>>::StateBackend,
-	>,
-) {
+fn import_block(mut client: &FullClient, built: BuiltBlock<node_primitives::Block>) {
 	let mut params = BlockImportParams::new(BlockOrigin::File, built.block.header);
 	params.state_action =
 		StateAction::ApplyChanges(sc_consensus::StorageChanges::Changes(built.storage_changes));

substrate/bin/node/cli/src/service.rs

@@ -140,7 +140,7 @@ pub fn new_partial(
 		FullClient,
 		FullBackend,
 		FullSelectChain,
-		sc_consensus::DefaultImportQueue<Block, FullClient>,
+		sc_consensus::DefaultImportQueue<Block>,
 		sc_transaction_pool::FullPool<Block, FullClient>,
 		(
 			impl Fn(