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

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

unspendables.pushKV("genesis_block", ValueFromAmount(stats.total_unspendables_genesis_block - prev_stats.total_unspendables_genesis_block));
            unspendables.pushKV("bip30", ValueFromAmount(stats.total_unspendables_bip30 - prev_stats.total_unspendables_bip30));
            unspendables.pushKV("scripts", ValueFromAmount(stats.total_unspendables_scripts - prev_stats.total_unspendables_scripts));
            unspendables.pushKV("unclaimed_rewards", ValueFromAmount(stats.total_unspendables_unclaimed_rewards - prev_stats.total_unspendables_unclaimed_rewards));
            block_info.pushKV("unspendables", unspendables);
            ret.pushKV("block_info", block_info);
        }
    } else {
        throw JSONRPCError(RPC_INTERNAL_ERROR, "Unable to read UTXO set");
    }
    return ret;
},
    };
}
static RPCHelpMan gettxout()
{
    return RPCHelpMan{"gettxout",
        "\nReturns details about an unspent transaction output.\n",
        {
            {"txid", RPCArg::Type::STR, RPCArg::Optional::NO, "The transaction id"},
            {"n", RPCArg::Type::NUM, RPCArg::Optional::NO, "vout number"},
            {"include_mempool", RPCArg::Type::BOOL, RPCArg::Default{true}, "Whether to include the mempool. Note that an unspent output that is spent in the mempool won't appear."},
        },
        {
            RPCResult{"If the UTXO was not found", RPCResult::Type::NONE, "", ""},
            RPCResult{"Otherwise", RPCResult::Type::OBJ, "", "", {
                {RPCResult::Type::STR_HEX, "bestblock", "The hash of the block at the tip of the chain"},
                {RPCResult::Type::NUM, "confirmations", "The number of confirmations"},
                {RPCResult::Type::STR_AMOUNT, "value", "The transaction value in " + CURRENCY_UNIT},
                {RPCResult::Type::OBJ, "scriptPubKey", "", {