Merge pull request #19365 from alalek:parallel_api

diff --cc modules/core/CMakeLists.txt
Simple merge

diff --cc samples/cpp/CMakeLists.txt
index 5f40dba,4f8977b..b378998
--- 1/samples/cpp/CMakeLists.txt
--- 2/samples/cpp/CMakeLists.txt
+++ b/samples/cpp/CMakeLists.txt
@@@ -33,11 -30,10 +33,12 @@@ if(NOT HAVE_opencv_cudaarithm OR NOT HA
    ocv_list_filterout(cpp_samples "/gpu/")
  endif()
  ocv_list_filterout(cpp_samples "real_time_pose_estimation/")
+ ocv_list_filterout(cpp_samples "parallel_backend/")
  foreach(sample_filename ${cpp_samples})
    set(package "cpp")
 -  if(sample_filename MATCHES "tutorial_code")
 +  if(sample_filename MATCHES "tutorial_code/snippet")
 +    set(package "snippet")
 +  elseif(sample_filename MATCHES "tutorial_code")
      set(package "tutorial")
    endif()
    ocv_define_sample(tgt ${sample_filename} ${package})