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/utils/frame/rpc/state-trie-migration-rpc/src/lib.rs

@@ -18,9 +18,9 @@
 //! Rpc for state migration.
 
 use jsonrpsee::{
-	core::{Error as JsonRpseeError, RpcResult},
+	core::RpcResult,
 	proc_macros::rpc,
-	types::error::{CallError, ErrorCode, ErrorObject},
+	types::error::{ErrorCode, ErrorObject, ErrorObjectOwned},
 };
 use sc_rpc_api::DenyUnsafe;
 use serde::{Deserialize, Serialize};
@@ -112,7 +112,7 @@ where
 }
 
 /// Current state migration status.
-#[derive(Serialize, Deserialize)]
+#[derive(Serialize, Deserialize, Clone)]
 #[serde(rename_all = "camelCase")]
 #[serde(deny_unknown_fields)]
 pub struct MigrationStatusResult {
@@ -168,10 +168,10 @@ where
 	}
 }
 
-fn error_into_rpc_err(err: impl std::fmt::Display) -> JsonRpseeError {
-	JsonRpseeError::Call(CallError::Custom(ErrorObject::owned(
+fn error_into_rpc_err(err: impl std::fmt::Display) -> ErrorObjectOwned {
+	ErrorObject::owned(
 		ErrorCode::InternalError.code(),
 		"Error while checking migration state",
 		Some(err.to_string()),
-	)))
+	)
 }