libdm: report: add dm_report_object_is_selected

libdm: report: add dm_report_object_is_selected

The new dm_report_object_is_selected fn makes it possible to opt whether the
object reported should be displayed on output or not. Also, in addition to
that, it makes it possible to save the result of selection (either 0 or 1).

So dm_report_object_is_selected is simply  more general form of object
reporting fn - combinations now allow for:

  dm_report_object_is_selected(rh, object, 1, NULL):
  This is exactly the original dm_report_object fn and it's fully equal
  to it.

  dm_report_object_is_selected(rh, object, 0, selected):
  Do not display the result on output, but save info whether the object
  is selected or not in 'selected' variable.

  dm_report_object_is_selected(rh, object, 1, selected):
  Display the result on output (if it passes selection criteria) and save
  whether the object is selected or not in 'selected' variable.

  dm_report_object(rh, object, 0, NULL):
  This combination is not allowed - it will end up with internal error.
  We're either interested in selection status or we want to display the
  result on output or both, but never nothing of the two.