Bring `getblockheader` up to date

[roylee17]

Missing chainwork, mediantime, and nTx attributes.

lbcctl getblockheader `lbcctl getblockhash 1000000` 1

On lbcd:

{
  "hash": "066d89a69aab2c1e3cb805aa4b2d1526d54758db8b657fa6ce22240afddb80fc",
  "confirmations": 176917,
  "height": 1000000,
  "version": 536870912,
  "versionHex": "20000000",
  "merkleroot": "57d5e9ee479f8568aa93fd438cbcffb742a2c9b9346fcd4df821d7987f60b00d",
  "time": 1627051164,
  "nonce": 74682161,
  "bits": "1a015eab",
  "difficulty": 802670066349.9366,
  "previousblockhash": "e13c26bf391ec0388ba7c530d18e224a2fa6416717d36befe11d6d46e5f37ca1",
  "nextblockhash": "cdfe317ad478ca72d9085bfe8d5ecfdf7e75a8cc0c2d14e66ba784e601730908"
}

On lbrycrd:

{
  "hash": "066d89a69aab2c1e3cb805aa4b2d1526d54758db8b657fa6ce22240afddb80fc",
  "confirmations": 176918,
  "height": 1000000,
  "version": 536870912,
  "versionHex": "20000000",
  "merkleroot": "57d5e9ee479f8568aa93fd438cbcffb742a2c9b9346fcd4df821d7987f60b00d",
  "nameclaimroot": "3dba16ea5516d36b7a2179697a8c99e28edac43b48609c809db95143c274b6a5",
  "time": 1627051164,
  "mediantime": 1627050190,
  "nonce": 74682161,
  "bits": "1a015eab",
  "difficulty": 802670066349.9366,
  "chainwork": "000000000000000000000000000000000000000000000565a6d2dac150305053",
  "nTx": 76,
  "previousblockhash": "e13c26bf391ec0388ba7c530d18e224a2fa6416717d36befe11d6d46e5f37ca1",
  "nextblockhash": "cdfe317ad478ca72d9085bfe8d5ecfdf7e75a8cc0c2d14e66ba784e601730908"
}