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.

unspent.pushKV("desc", descriptors[txo.scriptPubKey]);
            unspent.pushKV("amount", ValueFromAmount(txo.nValue));
            unspent.pushKV("height", (int32_t)coin.nHeight);
            unspents.push_back(unspent);
        }
        result.pushKV("unspents", unspents);
        result.pushKV("total_amount", ValueFromAmount(total_in));
    } else {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid command");
    }
    return result;
},
    };
}
static RPCHelpMan getblockfilter()
{
    return RPCHelpMan{"getblockfilter",
                "\nRetrieve a BIP 157 content filter for a particular block.\n",
                {
                    {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hash of the block"},
                    {"filtertype", RPCArg::Type::STR, RPCArg::Default{"basic"}, "The type name of the filter"},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::STR_HEX, "filter", "the hex-encoded filter data"},
                        {RPCResult::Type::STR_HEX, "header", "the hex-encoded filter header"},
                    }},
                RPCExamples{
                    HelpExampleCli("getblockfilter", "\"00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09\" \"basic\"") +