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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for (size_t i = 0; i < mtx.vout.size(); ++i) {
            const auto& txout = mtx.vout[i];
            bool is_mine = 0 < (wallet.IsMine(txout) & filter);
            changes += new_utxos[COutPoint(hash, i)] = is_mine ? txout.nValue : 0;
        }
    }
    UniValue result(UniValue::VOBJ);
    result.pushKV("balance_change", ValueFromAmount(changes));
    return result;
}
    };
}
static RPCHelpMan migratewallet()
{
    return RPCHelpMan{"migratewallet",
        "EXPERIMENTAL warning: This call may not work as expected and may be changed in future releases\n"
        "\nMigrate the wallet to a descriptor wallet.\n"
        "A new wallet backup will need to be made.\n"
        "\nThe migration process will create a backup of the wallet before migrating. This backup\n"
        "file will be named <wallet name>-<timestamp>.legacy.bak and can be found in the directory\n"
        "for this wallet. In the event of an incorrect migration, the backup can be restored using restorewallet."
        "\nEncrypted wallets must have the passphrase provided as an argument to this call.",
        {
            {"wallet_name", RPCArg::Type::STR, RPCArg::DefaultHint{"the wallet name from the RPC endpoint"}, "The name of the wallet to migrate. If provided both here and in the RPC endpoint, the two must be identical."},
            {"passphrase", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "The wallet passphrase"},
        },
        RPCResult{
            RPCResult::Type::OBJ, "", "",
            {
                {RPCResult::Type::STR, "wallet_name", "The name of the primary migrated wallet"},