Extract PartialComponents into a type alias (#2767)

Pulling PartialComponents into a named `Service` type stops clippy
complaining about type complexity and also makes the type signatures a
little less scary to read.

There's two instances where we can't pull it out into a type because a
nightly feature has not yet been stabilised (E.g. the `imp Fn` isn't
stabilised in a type alias context here:
https://github.com/paritytech/polkadot-sdk/blob/d84e135bbfc366a17bb6b72d0fc9d09ee781ab8d/polkadot/node/service/src/lib.rs#L477
).

---------

Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/bin/node-template/node/src/service.rs

@@ -23,29 +23,20 @@ type FullSelectChain = sc_consensus::LongestChain<FullBackend, Block>;
 /// imported and generated.
 const GRANDPA_JUSTIFICATION_PERIOD: u32 = 512;
 
-#[allow(clippy::type_complexity)]
-pub fn new_partial(
-	config: &Configuration,
-) -> Result<
-	sc_service::PartialComponents<
-		FullClient,
-		FullBackend,
-		FullSelectChain,
-		sc_consensus::DefaultImportQueue<Block>,
-		sc_transaction_pool::FullPool<Block, FullClient>,
-		(
-			sc_consensus_grandpa::GrandpaBlockImport<
-				FullBackend,
-				Block,
-				FullClient,
-				FullSelectChain,
-			>,
-			sc_consensus_grandpa::LinkHalf<Block, FullClient, FullSelectChain>,
-			Option<Telemetry>,
-		),
-	>,
-	ServiceError,
-> {
+pub type Service = sc_service::PartialComponents<
+	FullClient,
+	FullBackend,
+	FullSelectChain,
+	sc_consensus::DefaultImportQueue<Block>,
+	sc_transaction_pool::FullPool<Block, FullClient>,
+	(
+		sc_consensus_grandpa::GrandpaBlockImport<FullBackend, Block, FullClient, FullSelectChain>,
+		sc_consensus_grandpa::LinkHalf<Block, FullClient, FullSelectChain>,
+		Option<Telemetry>,
+	),
+>;
+
+pub fn new_partial(config: &Configuration) -> Result<Service, ServiceError> {
 	let telemetry = config
 		.telemetry_endpoints
 		.clone()