Do not call initialize_block before any runtime api (#8953)

* Do not call `initialize_block` before any runtime api

Before this change we always called `initialize_block` before calling
into the runtime. There was already support with `skip_initialize` to skip
the initialization. Almost no runtime_api requires that
`initialize_block` is called before. Actually this only leads to higher
execution times most of the time, because all runtime modules are
initialized and this is especially expensive when the block contained a
runtime upgrade.

TLDR: Do not call `initialize_block` before calling a runtime api.

* Change `validate_transaction` interface

* Fix rpc test

* Fixes and comments

* Some docs

substrate/primitives/transaction-pool/src/runtime_api.rs

@@ -22,22 +22,32 @@ use sp_runtime::traits::Block as BlockT;
 
 sp_api::decl_runtime_apis! {
 	/// The `TaggedTransactionQueue` api trait for interfering with the transaction queue.
-	#[api_version(2)]
+	#[api_version(3)]
 	pub trait TaggedTransactionQueue {
 		/// Validate the transaction.
 		#[changed_in(2)]
 		fn validate_transaction(tx: <Block as BlockT>::Extrinsic) -> TransactionValidity;
 
+		/// Validate the transaction.
+		#[changed_in(3)]
+		fn validate_transaction(
+			source: TransactionSource,
+			tx: <Block as BlockT>::Extrinsic,
+		) -> TransactionValidity;
+
 		/// Validate the transaction.
 		///
 		/// This method is invoked by the transaction pool to learn details about given transaction.
 		/// The implementation should make sure to verify the correctness of the transaction
-		/// against current state.
+		/// against current state. The given `block_hash` corresponds to the hash of the block
+		/// that is used as current state.
+		///
 		/// Note that this call may be performed by the pool multiple times and transactions
 		/// might be verified in any possible order.
 		fn validate_transaction(
 			source: TransactionSource,
 			tx: <Block as BlockT>::Extrinsic,
+			block_hash: Block::Hash,
 		) -> TransactionValidity;
 	}
 }