BlockId removal: refactor: HeaderBackend::header (#12874)

* BlockId removal: refactor: HeaderBackend::header

It changes the arguments of:
- `HeaderBackend::header`,
- `Client::header`,
- `PeersClient::header`
- `ChainApi::block_header`

methods from: `BlockId<Block>` to: `Block::Hash`

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

* non-trivial usages of haeder(block_id) refactored

This may required introduction of dedicated function:
header_for_block_num

* fmt

* fix

* doc fixed

* ".git/.scripts/fmt.sh"

* BlockId removal: refactor: HeaderBackend::expect_header

It changes the arguments of `HeaderBackend::expect_header` method from: `BlockId<Block>` to: `Block::Hash`

* ".git/.scripts/fmt.sh"

* readme updated

* ".git/.scripts/fmt.sh"

* fix

Co-authored-by: parity-processbot <>

substrate/client/service/src/builder.rs

@@ -70,10 +70,7 @@ use sp_consensus::block_validation::{
 };
 use sp_core::traits::{CodeExecutor, SpawnNamed};
 use sp_keystore::{CryptoStore, SyncCryptoStore, SyncCryptoStorePtr};
-use sp_runtime::{
-	generic::BlockId,
-	traits::{Block as BlockT, BlockIdTo, NumberFor, Zero},
-};
+use sp_runtime::traits::{Block as BlockT, BlockIdTo, NumberFor, Zero};
 use std::{str::FromStr, sync::Arc, time::SystemTime};
 
 /// Full client type.
@@ -479,7 +476,7 @@ where
 
 	sp_session::generate_initial_session_keys(
 		client.clone(),
-		&BlockId::Hash(chain_info.best_hash),
+		chain_info.best_hash,
 		config.dev_key_seed.clone().map(|s| vec![s]).unwrap_or_default(),
 	)
 	.map_err(|e| Error::Application(Box::new(e)))?;