[3.2] Backport of the cleos validate signatures

[ndcgundlach]

EOSIO/eos#9068

This sub-command takes a signed transaction, validates the signatures on it, and outputs a JSON array of the recovered public keys.

cleos validate signatures <json_file_of_transaction>

Example:

./cleos create account -j -d --json-file t eosio kevinh EOS6MRyAjQq8ud7hVNYcfnVPJqcVpscN5So8BhtHuGYqET5GDW5CV EOS6MRyAjQq8ud7hVNYcfnVPJqcVpscN5So8BhtHuGYqET5GDW5CV
{
  "expiration": "2022-06-23T00:50:08",
  "ref_block_num": 4714,
  "ref_block_prefix": 3530990,
  "max_net_usage_words": 0,
  "max_cpu_usage_ms": 0,
  "delay_sec": 0,
  "context_free_actions": [],
  "actions": [{
      "account": "eosio",
      "name": "newaccount",
      "authorization": [{
          "actor": "eosio",
          "permission": "active"
        }
      ],
      "data": "0000000000ea305500000000b4e9b68201000000010002c0ded2bc1f1305fb0faac5e6c03ee3a1924234985427b6167ca569d13df435cf0100000001000000010002c0ded2bc1f1305fb0faac5e6c03ee3a1924234985427b6167ca569d13df435cf01000000"
    }
  ],
  "transaction_extensions": [],
  "signatures": [
    "SIG_K1_K4ewr6ZLtiWABNKjEhWzXkfgiPdhpF2nKvGz9NKAGaZwtpKdBP6FBXrzKDpuiqEVfh5tZ4GAd4FcFZK4ysMf7NcgtreKfK"
  ],
  "context_free_data": []
}

./cleos validate signatures t
info  2022-06-23T00:49:48.284 cleos     main.cpp:2690                 operator()           ] grabbing chain_id from nodeos
[
  "EOS6MRyAjQq8ud7hVNYcfnVPJqcVpscN5So8BhtHuGYqET5GDW5CV"
]

Resolves: #401