Rpc for pending rewards (#11831)

* rpc pending rewards

* commit

* remove unused imports

* fix

* fix

* fmt

* fix

* fmt

* fix

* docs

* docs & formatting

* better formatting

* temporary fix

* error handling

* fix?

* fmt

* use to_string

* fmt

* fixed error handling

* fix

* rpc added to client

* Update Cargo.toml

* Update Cargo.toml

* fix wrong reward counter

* expose function

* move implementation

* docs

* docs

* docs

* Update lib.rs

* Update lib.rs

* unexpose functions

* unused dependency

* update Cargo.lock

* Update frame/nomination-pools/src/lib.rs

* Update lib.rs

* Update lib.rs

* Update frame/nomination-pools/rpc/runtime-api/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* remove rpc

* remove rpc directory

* final fix

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/Cargo.lock

@@ -4759,6 +4759,7 @@ dependencies = [
  "pallet-multisig",
  "pallet-nomination-pools",
  "pallet-nomination-pools-benchmarking",
+ "pallet-nomination-pools-runtime-api",
  "pallet-offences",
  "pallet-offences-benchmarking",
  "pallet-preimage",
@@ -5911,6 +5912,15 @@ dependencies = [
  "sp-std",
 ]
 
+[[package]]
+name = "pallet-nomination-pools-runtime-api"
+version = "1.0.0-dev"
+dependencies = [
+ "parity-scale-codec",
+ "sp-api",
+ "sp-std",
+]
+
 [[package]]
 name = "pallet-nomination-pools-test-staking"
 version = "1.0.0"