Transaction pool: Ensure that we prune transactions properly (#8963)

* Transaction pool: Ensure that we prune transactions properly

There was a bug in the transaction pool that we didn't pruned
transactions properly because we called `prune_known`, instead of `prune`.

This bug was introduced by:
https://github.com/paritytech/substrate/pull/4629

This is required to have stale extrinsics being removed properly, so
that they don't fill up the tx pool.

* Fix compilation

* Fix benches

* ...

substrate/client/transaction-pool/graph/benches/basics.rs

@@ -23,7 +23,7 @@ use sc_transaction_graph::*;
 use codec::Encode;
 use substrate_test_runtime::{Block, Extrinsic, Transfer, H256, AccountId};
 use sp_runtime::{
-	generic::BlockId,
+	generic::BlockId, traits::Block as BlockT,
 	transaction_validity::{
 		ValidTransaction, InvalidTransaction, TransactionValidity, TransactionTag as Tag,
 		TransactionSource,
@@ -114,6 +114,13 @@ impl ChainApi for TestApi {
 	fn block_body(&self, _id: &BlockId<Self::Block>) -> Self::BodyFuture {
 		ready(Ok(None))
 	}
+
+	fn block_header(
+		&self,
+		_: &BlockId<Self::Block>,
+	) -> Result<Option<<Self::Block as BlockT>::Header>, Self::Error> {
+		Ok(None)
+	}
 }
 
 fn uxt(transfer: Transfer) -> Extrinsic {