Revalidation queue for transaction pool (#4781)

* Revalidation queeue.

* add docs and license

* move test

* refactor worker to async/await

* address review

* fix warnings

* update Cargo.lock

* move background task to service

* use tomusdrw loop

* naming

* return From::from

* add doc comment

* add more doc comments

* fix merge bug

* add doc comment for test function

* Update client/transaction-pool/src/testing/pool.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* more review fixes

* refactor to allow service keep background tasks from isntantiated subsystems

* use const delay

* fix fallout

* remove fallout

* remove already moved test

* fix doc test

* add valid_at helper

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

substrate/client/transaction-pool/graph/src/validated_pool.rs

@@ -32,7 +32,7 @@ use parking_lot::{Mutex, RwLock};
 use sp_runtime::{
 	generic::BlockId,
 	traits::{self, SaturatedConversion},
-	transaction_validity::TransactionTag as Tag,
+	transaction_validity::{TransactionTag as Tag, ValidTransaction},
 };
 use sp_transaction_pool::{error, PoolStatus};
 use wasm_timer::Instant;
@@ -53,6 +53,30 @@ pub enum ValidatedTransaction<Hash, Ex, Error> {
 	Unknown(Hash, Error),
 }
 
+impl<Hash, Ex, Error> ValidatedTransaction<Hash, Ex, Error> {
+	/// Consume validity result, transaction data and produce ValidTransaction.
+	pub fn valid_at(
+		at: u64,
+		hash: Hash,
+		data: Ex,
+		bytes: usize,
+		validity: ValidTransaction,
+	) -> Self {
+		Self::Valid(base::Transaction {
+			data,
+			bytes,
+			hash,
+			priority: validity.priority,
+			requires: validity.requires,
+			provides: validity.provides,
+			propagate: validity.propagate,
+			valid_till: at
+				.saturated_into::<u64>()
+				.saturating_add(validity.longevity),
+		})
+	}
+}
+
 /// A type of validated transaction stored in the pool.
 pub type ValidatedTransactionFor<B> = ValidatedTransaction<
 	ExHash<B>,