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.

{RPCResult::Type::OBJ, "block_info",  true, "Info on amounts in the block at this block height (only available if coinstatsindex is used)",
                        {
                            {RPCResult::Type::STR_AMOUNT, "prevout_spent", "Total amount of all prevouts spent in this block"},
                            {RPCResult::Type::STR_AMOUNT, "coinbase", "Coinbase subsidy amount of this block"},
                            {RPCResult::Type::STR_AMOUNT, "new_outputs_ex_coinbase", "Total amount of new outputs created by this block"},
                            {RPCResult::Type::STR_AMOUNT, "unspendable", "Total amount of unspendable outputs created in this block"},
                            {RPCResult::Type::OBJ, "unspendables", "Detailed view of the unspendable categories",
                            {
                                {RPCResult::Type::STR_AMOUNT, "genesis_block", "The unspendable amount of the Genesis block subsidy"},
                                {RPCResult::Type::STR_AMOUNT, "bip30", "Transactions overridden by duplicates (no longer possible with BIP30)"},
                                {RPCResult::Type::STR_AMOUNT, "scripts", "Amounts sent to scripts that are unspendable (for example OP_RETURN outputs)"},
                                {RPCResult::Type::STR_AMOUNT, "unclaimed_rewards", "Fee rewards that miners did not claim in their coinbase transaction"},
                            }}
                        }},
                    }},
                RPCExamples{
                    HelpExampleCli("gettxoutsetinfo", "") +
                    HelpExampleCli("gettxoutsetinfo", R"("none")") +
                    HelpExampleCli("gettxoutsetinfo", R"("none" 1000)") +
                    HelpExampleCli("gettxoutsetinfo", R"("none" '"00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09"')") +
                    HelpExampleRpc("gettxoutsetinfo", "") +
                    HelpExampleRpc("gettxoutsetinfo", R"("none")") +
                    HelpExampleRpc("gettxoutsetinfo", R"("none", 1000)") +
                    HelpExampleRpc("gettxoutsetinfo", R"("none", "00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09")")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    UniValue ret(UniValue::VOBJ);
    CBlockIndex* pindex{nullptr};
    const CoinStatsHashType hash_type{request.params[0].isNull() ? CoinStatsHashType::HASH_SERIALIZED : ParseHashType(request.params[0].get_str())};