Support batching multiple RPC requests

[DelevoXDG]

Feature Request

Allow batching multiple RPC calls within the same request.
The nodes are accepting the array of RPC calls and they execute them all in parallel.

from tg:

Here is an example on goerli calling balanceOf (for 2 accounts) on the DAI token contract

[
 {
 "jsonrpc": "2.0",
 "id": "1",
 "method": "starknet_call",
 "params": [
  {
   "contract_address": "0x123",
   "entry_point_selector": "0x456",
   "calldata": [
    "0x1"
   ]
  },
   "pending"
  ]
 },
 {
  "jsonrpc": "2.0",
  "id": "2",
  "method": "starknet_call",
  "params": [
   {
    "contract_address": "0x123",
    "entry_point_selector": "0x456",
    "calldata": [
     "0x2"
    ]
   },
   "pending"
  ]
 }
]