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.

{
    return RPCHelpMan{"waitforblockheight",
                "\nWaits for (at least) block height and returns the height and hash\n"
                "of the current tip.\n"
                "\nReturns the current block on timeout or exit.\n",
                {
                    {"height", RPCArg::Type::NUM, RPCArg::Optional::NO, "Block height to wait for."},
                    {"timeout", RPCArg::Type::NUM, RPCArg::Default{0}, "Time in milliseconds to wait for a response. 0 indicates no timeout."},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::STR_HEX, "hash", "The blockhash"},
                        {RPCResult::Type::NUM, "height", "Block height"},
                    }},
                RPCExamples{
                    HelpExampleCli("waitforblockheight", "100 1000")
            + HelpExampleRpc("waitforblockheight", "100, 1000")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    int timeout = 0;
    int height = request.params[0].get_int();
    if (!request.params[1].isNull())
        timeout = request.params[1].get_int();
    CUpdatedBlock block;
    {
        WAIT_LOCK(cs_blockchange, lock);
        if(timeout)