rpc: backpressured RPC server (bump jsonrpsee 0.20) (#1313)

This is a rather big change in jsonrpsee, the major things in this bump
are:
- Server backpressure (the subscription impls are modified to deal with
that)
- Allow custom error types / return types (remove jsonrpsee::core::Error
and jsonrpee::core::CallError)
- Bug fixes (graceful shutdown in particular not used by substrate
anyway)
   - Less dependencies for the clients in particular
   - Return type requires Clone in method call responses
   - Moved to tokio channels
   - Async subscription API (not used in this PR)

Major changes in this PR:
- The subscriptions are now bounded and if subscription can't keep up
with the server it is dropped
- CLI: add parameter to configure the jsonrpc server bounded message
buffer (default is 64)
- Add our own subscription helper to deal with the unbounded streams in
substrate

The most important things in this PR to review is the added helpers
functions in `substrate/client/rpc/src/utils.rs` and the rest is pretty
much chore.

Regarding the "bounded buffer limit" it may cause the server to handle
the JSON-RPC calls
slower than before.

The message size limit is bounded by "--rpc-response-size" thus "by
default 10MB * 64 = 640MB"
but the subscription message size is not covered by this limit and could
be capped as well.

Hopefully the last release prior to 1.0, sorry in advance for a big PR

Previous attempt: https://github.com/paritytech/substrate/pull/13992

Resolves https://github.com/paritytech/polkadot-sdk/issues/748, resolves
https://github.com/paritytech/polkadot-sdk/issues/627

substrate/client/rpc/src/dev/mod.rs

@@ -22,7 +22,6 @@
 #[cfg(test)]
 mod tests;
 
-use jsonrpsee::core::RpcResult;
 use sc_client_api::{BlockBackend, HeaderBackend};
 use sc_rpc_api::{dev::error::Error, DenyUnsafe};
 use sp_api::{ApiExt, Core, ProvideRuntimeApi};
@@ -65,7 +64,7 @@ where
 		+ 'static,
 	Client::Api: Core<Block>,
 {
-	fn block_stats(&self, hash: Block::Hash) -> RpcResult<Option<BlockStats>> {
+	fn block_stats(&self, hash: Block::Hash) -> Result<Option<BlockStats>, Error> {
 		self.deny_unsafe.check_if_safe()?;
 
 		let block = {

substrate/client/rpc/src/dev/tests.rs

@@ -97,7 +97,7 @@ async fn deny_unsafe_works() {
 		"{{\"jsonrpc\":\"2.0\",\"method\":\"dev_getBlockStats\",\"params\":[{}],\"id\":1}}",
 		best_hash_param
 	);
-	let (resp, _) = api.raw_json_request(&request).await.expect("Raw calls should succeed");
+	let (resp, _) = api.raw_json_request(&request, 1).await.expect("Raw calls should succeed");
 
 	assert_eq!(
 		resp.result,