rpcserver: add parity with bitcoind for validateaddress

[onyb]

What is this about?

Updated the rpcserver handler for validateaddress JSON-RPC command to have parity with the bitcoind 0.20.0 interface.

The new fields included are - isscript, iswitness, witness_version, and witness_program. The scriptPubKey field has been left out since it requires wallet access.

This update has no impact on the rpcclient.ValidateAddress method, which uses the btcjson.ValidateAddressWalletResult type for modelling the response from bitcoind.

How to test?

Unfortunately, we lack a proper framework to write rpcserver tests, so here's you can test this PR:

Prepare

$ go build .
$ ./btcd --testnet --rpcuser=aaaa --rpcpass=bbbb

In another tab,

$ cd cmd/btcctl
$ go build .

P2PKH valid

$ ./btcctl --testnet --rpcuser=aaaa --rpcpass=bbbb validateaddress mkpZhYtJu2r87Js3pDiWJDmPte2NRZ8bJV
{
  "isvalid": true,
  "address": "mkpZhYtJu2r87Js3pDiWJDmPte2NRZ8bJV",
  "isscript": false,
  "iswitness": false
}

P2SH-P2WPKH valid

$ ./btcctl --testnet --rpcuser=aaaa --rpcpass=bbbb validateaddress 2N4Q5FhU2497BryFfUgbqkAJE87aKHUhXMp
{
  "isvalid": true,
  "address": "2N4Q5FhU2497BryFfUgbqkAJE87aKHUhXMp",
  "isscript": true,
  "iswitness": false
}

P2WPKH valid

$ ./btcctl --testnet --rpcuser=aaaa --rpcpass=bbbb validateaddress tb1qkwgskuzmmwwvqajnyr7yp9hgvh5y45kg8wvdmd
{
  "isvalid": true,
  "address": "tb1qkwgskuzmmwwvqajnyr7yp9hgvh5y45kg8wvdmd",
  "isscript": false,
  "iswitness": true,
  "witness_version": 0,
  "witness_program": "b3910b705bdb9cc0765320fc4096e865e84ad2c8"
}

Invalid address

$ ./btcctl --testnet --rpcuser=aaaa --rpcpass=bbbb validateaddress deadbeef
{
  "isvalid": false
}

Invalid network

$ ./btcctl --testnet --rpcuser=aaaa --rpcpass=bbbb validateaddress 1MirQ9bwyQcGVJPwKUgapu5ouK2E2Ey4gX
{
  "isvalid": false
}

[Rjected]

The code looks good to me, I tested as well and did not have any issues.

[jakesylvestre]

Looks good to me.

[jcvernaleo]

OK