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-spec-v2/src/chain_head/api.rs

@@ -20,10 +20,13 @@
 
 //! API trait of the chain head.
 use crate::{
-	chain_head::event::{FollowEvent, MethodResponse},
+	chain_head::{
+		error::Error,
+		event::{FollowEvent, MethodResponse},
+	},
 	common::events::StorageQuery,
 };
-use jsonrpsee::{core::RpcResult, proc_macros::rpc};
+use jsonrpsee::proc_macros::rpc;
 use sp_rpc::list::ListOrValue;
 
 #[rpc(client, server)]
@@ -56,7 +59,7 @@ pub trait ChainHeadApi<Hash> {
 		&self,
 		follow_subscription: String,
 		hash: Hash,
-	) -> RpcResult<MethodResponse>;
+	) -> Result<MethodResponse, Error>;
 
 	/// Retrieves the header of a pinned block.
 	///
@@ -75,7 +78,7 @@ pub trait ChainHeadApi<Hash> {
 		&self,
 		follow_subscription: String,
 		hash: Hash,
-	) -> RpcResult<Option<String>>;
+	) -> Result<Option<String>, Error>;
 
 	/// Returns storage entries at a specific block's state.
 	///
@@ -89,7 +92,7 @@ pub trait ChainHeadApi<Hash> {
 		hash: Hash,
 		items: Vec<StorageQuery<String>>,
 		child_trie: Option<String>,
-	) -> RpcResult<MethodResponse>;
+	) -> Result<MethodResponse, Error>;
 
 	/// Call into the Runtime API at a specified block's state.
 	///
@@ -103,7 +106,7 @@ pub trait ChainHeadApi<Hash> {
 		hash: Hash,
 		function: String,
 		call_parameters: String,
-	) -> RpcResult<MethodResponse>;
+	) -> Result<MethodResponse, Error>;
 
 	/// Unpin a block or multiple blocks reported by the `follow` method.
 	///
@@ -120,7 +123,7 @@ pub trait ChainHeadApi<Hash> {
 		&self,
 		follow_subscription: String,
 		hash_or_hashes: ListOrValue<Hash>,
-	) -> RpcResult<()>;
+	) -> Result<(), Error>;
 
 	/// Resumes a storage fetch started with `chainHead_storage` after it has generated an
 	/// `operationWaitingForContinue` event.
@@ -133,7 +136,7 @@ pub trait ChainHeadApi<Hash> {
 		&self,
 		follow_subscription: String,
 		operation_id: String,
-	) -> RpcResult<()>;
+	) -> Result<(), Error>;
 
 	/// Stops an operation started with chainHead_unstable_body, chainHead_unstable_call, or
 	/// chainHead_unstable_storage. If the operation was still in progress, this interrupts it. If
@@ -147,5 +150,5 @@ pub trait ChainHeadApi<Hash> {
 		&self,
 		follow_subscription: String,
 		operation_id: String,
-	) -> RpcResult<()>;
+	) -> Result<(), Error>;
 }