Add bulk request for slot information

[rbx]

When asking for slot info currently the info is delivered one by one:

SSlotInfoRequest::request_t requestInfo;
SSlotInfoRequest::ptr_t requestPtr{ SSlotInfoRequest::makeRequest(requestInfo) };

requestPtr->setResponseCallback([](const SSlotInfoResponseData& _info) {
    LOG(log_stdout_clean) << "Slot " << _info.m_index << ": agentID (" << _info.m_agentID << "), slotID ("
                          << _info.m_slotID << "), taskID (" << _info.m_taskID << "), state (" << _info.m_state
                          << "), host (" << _info.m_host << "), wrkDir (" << quoted(_info.m_wrkDir) << ")";
});

For many slots it would be more efficient (at least on the user side) to get all slots in a bulk response.
As it is done in a similar request for agent info:

SAgentInfoRequest::request_t agentInfoRequest;
SAgentInfoRequest::responseVector_t agentInfo;
ddsSession->syncSendRequest<SAgentInfoRequest>(agentInfoRequest, agentInfo, timeout);