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* remove outdated comments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/blocks/blocks_client.rs

@@ -95,8 +95,8 @@ where
     {
         let client = self.client.clone();
         header_sub_fut_to_block_sub(self.clone(), async move {
-            let sub = client.backend().stream_all_block_headers().await?;
-            BlockStreamRes::Ok(sub)
+            let stream = client.backend().stream_all_block_headers().await?;
+            BlockStreamRes::Ok(stream)
         })
     }
 
@@ -112,8 +112,8 @@ where
     {
         let client = self.client.clone();
         header_sub_fut_to_block_sub(self.clone(), async move {
-            let sub = client.backend().stream_best_block_headers().await?;
-            BlockStreamRes::Ok(sub)
+            let stream = client.backend().stream_best_block_headers().await?;
+            BlockStreamRes::Ok(stream)
         })
     }
 
@@ -126,8 +126,8 @@ where
     {
         let client = self.client.clone();
         header_sub_fut_to_block_sub(self.clone(), async move {
-            let sub = client.backend().stream_finalized_block_headers().await?;
-            BlockStreamRes::Ok(sub)
+            let stream = client.backend().stream_finalized_block_headers().await?;
+            BlockStreamRes::Ok(stream)
         })
     }
 }