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

Cargo.lock

@@ -4557,7 +4557,6 @@ dependencies = [
  "subxt-signer",
  "thiserror",
  "tokio",
- "tokio-stream",
  "tokio-util",
  "tracing",
  "tracing-subscriber 0.3.18",
@@ -4617,7 +4616,6 @@ dependencies = [
 name = "subxt-lightclient"
 version = "0.34.0"
 dependencies = [
- "either",
  "futures",
  "futures-timer",
  "futures-util",