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-template/node/src/service.rs

@@ -49,7 +49,7 @@ pub fn new_partial(
 		FullClient,
 		FullBackend,
 		FullSelectChain,
-		sc_consensus::DefaultImportQueue<Block, FullClient>,
+		sc_consensus::DefaultImportQueue<Block>,
 		sc_transaction_pool::FullPool<Block, FullClient>,
 		(
 			sc_consensus_grandpa::GrandpaBlockImport<