Write proper toString implementation in UtHashMap

[alexeyfridman]

SAT-1604

String mapToString(long startTime, int pageSize, int pageNum) {
    Map<String, Object> params = new HashMap<>();

    params.put("startTime", startTime);
    params.put("pageSize", pageSize);
    params.put("pageNum", pageNum);

    return params.toString();
}

For now we have the following implementation:

    @Override
    public String toString() {
        executeConcretely();
        return super.toString();
    }

We should implement it without executionConcretely

Common issue for collections toString method, especially huge collections