Bring `getrawmempool` up to date

[roylee17]

ancestor* descendant* attributes are currently mocked with the transaction itself, not from the actual ancestors/descendants.

$ lbrycrd-cli getrawmempool true > lbrycrd-getrawmempool.json

 "016c84d9bf2d1d6e134b513fc03878847ae2a8fe310aea0a399d8518202ddefa": {
    "fees": {
      "base": 0.00114100,
      "modified": 0.00114100,
      "ancestor": 0.00114100,
      "descendant": 0.00114100
    },
    "size": 2259,
    "fee": 0.00114100,
    "modifiedfee": 0.00114100,
    "time": 1644594445,
    "height": 1110043,
    "descendantcount": 1,
    "descendantsize": 2259,
    "descendantfees": 114100,
    "ancestorcount": 1,
    "ancestorsize": 2259,
    "ancestorfees": 114100,
    "wtxid": "016c84d9bf2d1d6e134b513fc03878847ae2a8fe310aea0a399d8518202ddefa",
    "depends": [
    ],
    "spentby": [
    ]
  },
...

$  lbcctl getrawmempool true > lbcd-getrawmempool.json

  "016c84d9bf2d1d6e134b513fc03878847ae2a8fe310aea0a399d8518202ddefa": {
    "size": 2259,
    "vsize": 2259,
    "weight": 9036,
    "fee": 0.001141,
    "time": 1644594446,
    "height": 1110043,
    "startingpriority": 55887613.765151516,
    "currentpriority": 55892328.428030305,
    "depends": []
  },
...

[roylee17]

Still have some fields to be populated in RawMempoolVerbose:

https://github.com/lbryio/lbcd/blob/master/mempool/mempool.go#L1510-L1545