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-api/src/chain/mod.rs

@@ -18,20 +18,21 @@
 
 //! Substrate blockchain API.
 
-use jsonrpsee::{core::RpcResult, proc_macros::rpc};
-use sp_rpc::{list::ListOrValue, number::NumberOrHex};
-
 pub mod error;
 
+use error::Error;
+use jsonrpsee::proc_macros::rpc;
+use sp_rpc::{list::ListOrValue, number::NumberOrHex};
+
 #[rpc(client, server)]
 pub trait ChainApi<Number, Hash, Header, SignedBlock> {
 	/// Get header.
 	#[method(name = "chain_getHeader", blocking)]
-	fn header(&self, hash: Option<Hash>) -> RpcResult<Option<Header>>;
+	fn header(&self, hash: Option<Hash>) -> Result<Option<Header>, Error>;
 
 	/// Get header and body of a block.
 	#[method(name = "chain_getBlock", blocking)]
-	fn block(&self, hash: Option<Hash>) -> RpcResult<Option<SignedBlock>>;
+	fn block(&self, hash: Option<Hash>) -> Result<Option<SignedBlock>, Error>;
 
 	/// Get hash of the n-th block in the canon chain.
 	///
@@ -40,11 +41,11 @@ pub trait ChainApi<Number, Hash, Header, SignedBlock> {
 	fn block_hash(
 		&self,
 		hash: Option<ListOrValue<NumberOrHex>>,
-	) -> RpcResult<ListOrValue<Option<Hash>>>;
+	) -> Result<ListOrValue<Option<Hash>>, Error>;
 
 	/// Get hash of the last finalized block in the canon chain.
 	#[method(name = "chain_getFinalizedHead", aliases = ["chain_getFinalisedHead"], blocking)]
-	fn finalized_head(&self) -> RpcResult<Hash>;
+	fn finalized_head(&self) -> Result<Hash, Error>;
 
 	/// All head subscription.
 	#[subscription(