add Serai JSON-RPC methods (#627)

* add serai rpc methods

* fix machete & dex quote price api

* fix validators api

---------

Co-authored-by: Luke Parker <lukeparker5132@gmail.com>

Cargo.lock

@@ -9421,7 +9421,9 @@ dependencies = [
  "jsonrpsee",
  "libp2p 0.52.4",
  "log",
+ "monero-wallet",
  "pallet-transaction-payment-rpc",
+ "parity-scale-codec",
  "rand_core",
  "sc-authority-discovery",
  "sc-basic-authorship",
@@ -9893,7 +9895,6 @@ dependencies = [
  "serai-dex-pallet",
  "serai-primitives",
  "serai-validator-sets-primitives",
- "serde",
  "sp-application-crypto",
  "sp-consensus-babe",
  "sp-core",