Some wallet calls (like getbalances) need to lock the chainstate to make sure they are caught up on the latest block (which may have been reported to the users in getblockchaininfo or similar).

Those calls could benefit if the block hash they were valid on was included in the response. For example, immature balance can only change when the chainstate changes. (Assuming no keys are imported)

It seems those calls can include the block hash they are caught up with for free in the response. They could simply include `m_last_block_processed` in the response.

I haven't checked back with other developers to see if they like this approach, but to start simple only a single call could be updated for now. E.g. `getbalances`.

#### Useful skills:

Basic understanding of threads, the Bitcoin Core wallet and the Bitcoin Core RPC interface.

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}
    }
    
    if (nFrom > (int)ret.size())
        nFrom = ret.size();
    if ((nFrom + nCount) > (int)ret.size())
        nCount = ret.size() - nFrom;
    auto txs_rev_it{std::make_move_iterator(ret.rend())};
    UniValue result{UniValue::VARR};
    result.push_backV(txs_rev_it - nFrom - nCount, txs_rev_it - nFrom); 
    return result;
},
    };
}
RPCHelpMan listsinceblock()
{
    return RPCHelpMan{"listsinceblock",
                "\nGet all transactions in blocks since block [blockhash], or all transactions if omitted.\n"
                "If \"blockhash\" is no longer a part of the main chain, transactions from the fork point onward are included.\n"
                "Additionally, if include_removed is set, transactions affecting the wallet which were removed are returned in the \"removed\" array.\n",
                {
                    {"blockhash", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "If set, the block hash to list transactions since, otherwise list all transactions."},
                    {"target_confirmations", RPCArg::Type::NUM, RPCArg::Default{1}, "Return the nth block hash from the main chain. e.g. 1 would mean the best block hash. Note: this is not used as a filter, but only affects [lastblock] in the return value"},
                    {"include_watchonly", RPCArg::Type::BOOL, RPCArg::DefaultHint{"true for watch-only wallets, otherwise false"}, "Include transactions to watch-only addresses (see 'importaddress')"},
                    {"include_removed", RPCArg::Type::BOOL, RPCArg::Default{true}, "Show transactions that were removed due to a reorg in the \"removed\" array\n"
                                                                       "(not guaranteed to work on pruned nodes)"},
                    {"include_change", RPCArg::Type::BOOL, RPCArg::Default{false}, "Also add entries for change outputs.\n"},
                    {"label", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "Return only incoming transactions paying to addresses with the specified label.\n"},
                },
                RPCResult{