Decouples light-sync state from chain spec (#9491)

* Decouples light-sync state from chain spec

This decouples the light-sync state from chain spec. First, the
light-sync state currently only works with BABE+Grandpa, so not
all *Substrate* based chains can use this feature. The next problem was
also that this pulled the `sc-consensus-babe` and `sc-finality-grandpa`
crate into `sc-chain-spec`.

If a chain now wants to support the light-sync state, it needs to add
the `LightSyncStateExtension` to the chain spec as an extension. This is
documented in the crate level docs of `sc-sync-state-rpc`. If this
extension is not available, `SyncStateRpc` fails at initialization.

* Fix compilation for browser

* Fmt

substrate/bin/node/cli/src/service.rs

@@ -49,7 +49,10 @@ pub fn new_partial(
 		sc_consensus::DefaultImportQueue<Block, FullClient>,
 		sc_transaction_pool::FullPool<Block, FullClient>,
 		(
-			impl Fn(node_rpc::DenyUnsafe, sc_rpc::SubscriptionTaskExecutor) -> node_rpc::IoHandler,
+			impl Fn(
+				node_rpc::DenyUnsafe,
+				sc_rpc::SubscriptionTaskExecutor,
+			) -> Result<node_rpc::IoHandler, sc_service::Error>,
 			(
 				sc_consensus_babe::BabeBlockImport<Block, FullClient, FullGrandpaBlockImport>,
 				grandpa::LinkHalf<Block, FullClient, FullSelectChain>,
@@ -180,7 +183,7 @@ pub fn new_partial(
 				},
 			};
 
-			node_rpc::create_full(deps)
+			node_rpc::create_full(deps).map_err(Into::into)
 		};
 
 		(rpc_extensions_builder, rpc_setup)