Rework light client (#1475)

* WIP second pass over light client code for simpler API

* First pass new light client

* pub(crate) LightClientRpc::new_raw(), and fmt

* Update examples and add back a way to configure boot nodes and fetch chainspec from a URL

* Fix light client examples

* remove unused deps and tidy lightclient feature flags

* fix wasm error

* LightClientRpc can be cloned

* update light client tests

* Other small fixes

* exclude mod unless jsonrpsee

* Fix wasm-lightclient-tests

* add back docsrs bit and web+native feature flag compile error

* update book and light client example names

* fix docs

subxt/src/lib.rs

@@ -61,6 +61,11 @@ pub mod utils;
 #[macro_use]
 mod macros;
 
+// Expose light client bits
+cfg_unstable_light_client! {
+    pub use subxt_lightclient as lightclient;
+}
+
 // Expose a few of the most common types at root,
 // but leave most types behind their respective modules.
 pub use crate::{