rpc: add full support reconnecting rpc client (#1505)

* add simple reconnecting rpc client

* initial retryable calls

* add reconnecting backend

* add reconnecting example for unstable backend

* add todo what isn't working

* FollowStream: restart on reconn

* naive fix: fetch sub_id in stream_headers

* cleanup

* remove resubscribe APIs

* cleanup and remove many wrapper streams

* remove retry backend

* legacy rpc: make it retryable

* unstable rpc: make it retryable

* fix nits

* support wasm as well

* remove deadcode

* address grumbles

* revert rpc methods

* don't create a subscription per block

* get rid off retry logic in subxt rpc

* Update subxt/Cargo.toml

* Update subxt/src/backend/legacy/mod.rs

* Update subxt/src/backend/legacy/mod.rs

* remove outdated comments

* fix bad merge

* Fix reconnecting RPC client and update dependencies

* add back retry logic and remove `finito`

* fix nits

* cleanup

* add hack for race when reconnecting

* backend: emit Stop event DisconnectWillRecoonect

* merge reconnecting client examples

* add fn retry_stream

* cleanup

* add all features from reconnecting-rpc-client

* fix build

* remove needless retry for fetch_storage

* StorageFetchDescendantKeysStream handle disconnect err

* dont retry transactions

* fetch subscription ID from FollowStreamMsg

* fix nits

* Update subxt/src/backend/legacy/mod.rs

* Update subxt/src/backend/legacy/mod.rs

* add reconn to StorageItems stream

* StorageFetchDescendantKeysStreamchore: retry storage call

* RetryStream: emit DisconnectWillReconnect msg

* runtime subscriptions ignore DisconnectWillReconn

* Update subxt/examples/setup_reconnecting_rpc_client.rs

* Update subxt/src/client/online_client.rs

* Update subxt/src/client/online_client.rs

* Add custom stream wrapper for finalized blocks

* add missing retry block

* clippy

* clippy again

* cleanup

* remove duplicate logic

* fix more grumbles

* Update subxt/examples/setup_reconnecting_rpc_client.rs

Co-authored-by: James Wilson <james@jsdw.me>

* simplify the example

* remove pin-project dep

* remove duplicate retry logic

* remove extra code

* specify trait bounds for retry api

* simplify the example

* fix weird Poll::Pending return

* fix nit in poll impl

* remove needless paths

* make retry_stream pub and add doc examples

* Update subxt/src/backend/utils.rs

---------

Co-authored-by: James Wilson <james@jsdw.me>

subxt/src/client/online_client.rs

@@ -432,9 +432,8 @@ impl<T: Config> ClientRuntimeUpdater<T> {
     /// Instead that's up to the user of this API to decide when to update and
     /// to perform the actual updating.
     pub async fn runtime_updates(&self) -> Result<RuntimeUpdaterStream<T>, Error> {
-        let stream = self.0.backend().stream_runtime_version().await?;
         Ok(RuntimeUpdaterStream {
-            stream,
+            stream: self.0.backend().stream_runtime_version().await?,
             client: self.0.clone(),
         })
     }