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/client/chain-spec/derive/src/impls.rs

@@ -65,6 +65,15 @@ pub fn extension_derive(ast: &DeriveInput) -> proc_macro::TokenStream {
 						_ => self,
 					}
 				}
+
+				fn get_any_mut(&mut self, t: std::any::TypeId) -> &mut dyn std::any::Any {
+					use std::any::{Any, TypeId};
+
+					match t {
+						#( x if x == TypeId::of::<#field_types>() => &mut self.#field_names ),*,
+						_ => self,
+					}
+				}
 			}
 		}
 	})