BlockId removal: refactor: Backend::begin_state_operation (#12541)

It changes the arguments of `Backend::begin_state_operation`
from: block: `BlockId<Block>` to: hash: `&Block::Hash`

This PR is part of BlockId::Number refactoring analysis (paritytech/substrate#11292)

substrate/client/api/src/backend.rs

@@ -467,7 +467,7 @@ pub trait Backend<Block: BlockT>: AuxStore + Send + Sync {
 	fn begin_state_operation(
 		&self,
 		operation: &mut Self::BlockImportOperation,
-		block: BlockId<Block>,
+		block: &Block::Hash,
 	) -> sp_blockchain::Result<()>;
 
 	/// Commit block insertion.

substrate/client/api/src/in_mem.rs

@@ -695,10 +695,9 @@ where
 	fn begin_state_operation(
 		&self,
 		operation: &mut Self::BlockImportOperation,
-		block: BlockId<Block>,
+		block: &Block::Hash,
 	) -> sp_blockchain::Result<()> {
-		let hash = self.blockchain.expect_block_hash_from_id(&block)?;
-		operation.old_state = self.state_at(&hash)?;
+		operation.old_state = self.state_at(block)?;
 		Ok(())
 	}