add chain supply, transparent and burned coins value pools

[DeckerSU]

This PR introduces transparent and burned value pools to the getblockchaininfo and getblock RPC output. This allows you to view the total value statistics of the transparent value pool up to and including the last (or given) block, as well as the same statistics for burned (with OP_RETURN) coins, etc. To enable this monitoring, you'll need to either sync the chain from scratch or reindex the existing blockchain. Please note that after running a version of the daemon with these changes, it's not recommended to revert to an older version of the daemon using the same blockchain data folder. This is because the newer version introduces changes in the CDiskBlockIndex (de)serialization.

The example of such statistics output for getblockchaininfo:

  "chainSupply": {
    "monitored": true,
    "chainValue": 102275770.19701314,
    "chainValueZat": 10227577019701314
  },
  "valuePools": [
    {
      "id": "transparent",
      "monitored": true,
      "chainValue": 102358500.86915928,
      "chainValueZat": 10235850086915928
    },
    {
      "id": "sprout",
      "monitored": true,
      "chainValue": 1501.85954926,
      "chainValueZat": 150185954926
    },
    {
      "id": "sapling",
      "monitored": true,
      "chainValue": 0,
      "chainValueZat": 0
    },
    {
      "id": "burned",
      "monitored": true,
      "chainValue": 401213.55488257,
      "chainValueZat": 40121355488257
    }
  ],

Also, please note that the chainSupply amount only includes coinbase outputs and does not account for coins created by interest (rewards). This is why the values of chainSupply and transparent differ.

Burned coins refer to coins that are involved in transactions like the following:

{
  "txid": "e363f3ae4547dc4262d6e09c1a5113ac1d9d148320e61b03096f023a1a76053e",
  "overwintered": false,
  "version": 1,
  "locktime": 0,
  "vin": [
  ],
  "vout": [
    {
      "value": 1.00000000,
      "valueZat": 100000000,
      "n": 0,
      "scriptPubKey": {
        "asm": "OP_RETURN 6465636b6572",
        "hex": "6a066465636b6572",
        "type": "nulldata"
      }
    }
  ],
  "vjoinsplit": [
  ]
}

In the example above, we see the burning of 1 COIN as the OP_RETURN outputs are unspendable, meaning this coin is effectively burned.

Corresponding PR in KomodoOcean codebase: DeckerSU/KomodoOcean#65