[rpc module] test helper for calling and converting types to JSON-RPC params (#458)

* new helper for testing

* fix features

* call_with_params -> call_with

* call_with_params -> call_with

* Update utils/src/server/rpc_module.rs

* fix trait bound

* Update utils/src/server/rpc_module.rs

Co-authored-by: David <[email protected]>

* call_with -> test_call

* fix grumbles

* fix nits

Co-authored-by: David <[email protected]>