Refactor sr-api to not depend on client anymore (#4086)

* Refactor sr-api to not depend on client anymore

* Fix benches

* Apply suggestions from code review

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Apply suggestions from code review

substrate/srml/system/rpc/runtime-api/Cargo.toml

@@ -5,12 +5,12 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-client = { package = "substrate-client", path = "../../../../core/client", default-features = false }
+sr-api = { path = "../../../../core/sr-api", default-features = false }
 codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false  }
 
 [features]
 default = ["std"]
 std = [
-	"client/std",
+	"sr-api/std",
 	"codec/std",
 ]

substrate/srml/system/rpc/runtime-api/src/lib.rs

@@ -22,7 +22,7 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-client::decl_runtime_apis! {
+sr_api::decl_runtime_apis! {
 	/// The API to query account nonce (aka transaction index).
 	pub trait AccountNonceApi<AccountId, Index> where
 		AccountId: codec::Codec,