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/consensus/manual-seal/src/consensus.rs

@@ -30,9 +30,6 @@ pub mod timestamp;
 /// Consensus data provider, manual seal uses this trait object for authoring blocks valid
 /// for any runtime.
 pub trait ConsensusDataProvider<B: BlockT>: Send + Sync {
-	/// Block import transaction type
-	type Transaction;
-
 	/// The proof type.
 	type Proof;
 
@@ -43,7 +40,7 @@ pub trait ConsensusDataProvider<B: BlockT>: Send + Sync {
 	fn append_block_import(
 		&self,
 		parent: &B::Header,
-		params: &mut BlockImportParams<B, Self::Transaction>,
+		params: &mut BlockImportParams<B>,
 		inherents: &InherentData,
 		proof: Self::Proof,
 	) -> Result<(), Error>;