RPCs that return detailed information about mempool entries (e.g. `getmempoolentry` and `getrawmempool(verbose=True)` include the fields `fee`, `modifiedfee`, `descendantfees`, and `ancestorfees` which were marked as "DEPRECATED" and replaced with a `fees` object field in #12240 (since v0.17).

We should remove these fields, but first, properly deprecate them using `-deprecatedrpc`.

#### Useful skills:

- basic understanding of Bitcoin Core RPC interface

#### Want to work on this issue?

For guidance on contributing, please read [CONTRIBUTING.md](https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md) before opening your pull request.

}
        }
    }
    if (GetUTXOStats(coins_view, *blockman, stats, node.rpc_interruption_point, pindex)) {
        ret.pushKV("height", (int64_t)stats.nHeight);
        ret.pushKV("bestblock", stats.hashBlock.GetHex());
        ret.pushKV("txouts", (int64_t)stats.nTransactionOutputs);
        ret.pushKV("bogosize", (int64_t)stats.nBogoSize);
        if (hash_type == CoinStatsHashType::HASH_SERIALIZED) {
            ret.pushKV("hash_serialized_2", stats.hashSerialized.GetHex());
        }
        if (hash_type == CoinStatsHashType::MUHASH) {
              ret.pushKV("muhash", stats.hashSerialized.GetHex());
        }
        ret.pushKV("total_amount", ValueFromAmount(stats.nTotalAmount));
        if (!stats.index_used) {
            ret.pushKV("transactions", static_cast<int64_t>(stats.nTransactions));
            ret.pushKV("disk_size", stats.nDiskSize);
        } else {
            ret.pushKV("total_unspendable_amount", ValueFromAmount(stats.total_unspendable_amount));
            CCoinsStats prev_stats{hash_type};
            if (pindex->nHeight > 0) {
                GetUTXOStats(coins_view, *blockman, prev_stats, node.rpc_interruption_point, pindex->pprev);
            }
            UniValue block_info(UniValue::VOBJ);
            block_info.pushKV("prevout_spent", ValueFromAmount(stats.total_prevout_spent_amount - prev_stats.total_prevout_spent_amount));
            block_info.pushKV("coinbase", ValueFromAmount(stats.total_coinbase_amount - prev_stats.total_coinbase_amount));
            block_info.pushKV("new_outputs_ex_coinbase", ValueFromAmount(stats.total_new_outputs_ex_coinbase_amount - prev_stats.total_new_outputs_ex_coinbase_amount));
            block_info.pushKV("unspendable", ValueFromAmount(stats.total_unspendable_amount - prev_stats.total_unspendable_amount));
            UniValue unspendables(UniValue::VOBJ);