gapi: buildOpticalFlowPyramid() interface, CPUkernel and CPUtests implementation

- kernel added to a cv::gapi::video namespace
     - tests to check a kernels (based on cv::video tests for cv::buildOpticalFlowPyramid())
     - tests for a combined G-API-pipeline (buildOpticalFlowPyramid() -> calcOpticalFlowPyrLK())
     - tests for internal purposes added
     - custom function for comparison in tests implemented

modules/gapi/test/common/gapi_video_tests.hpp

@@ -11,6 +11,11 @@
 
 namespace opencv_test
 {
+GAPI_TEST_FIXTURE_SPEC_PARAMS(BuildOptFlowPyramidTest,
+                              FIXTURE_API(std::string,int,int,bool,int,int,bool), 7,
+                              fileName, winSize, maxLevel, withDerivatives, pyrBorder,
+                              derivBorder, tryReuseInputImage)
+
 GAPI_TEST_FIXTURE_SPEC_PARAMS(OptFlowLKTest, FIXTURE_API(std::string,int,tuple<int,int>,int,
                                                          cv::TermCriteria),
                               5, fileNamePattern, channels, pointsNum, winSize, criteria)
@@ -18,6 +23,11 @@ GAPI_TEST_FIXTURE_SPEC_PARAMS(OptFlowLKTest, FIXTURE_API(std::string,int,tuple<i
 GAPI_TEST_FIXTURE_SPEC_PARAMS(OptFlowLKTestForPyr, FIXTURE_API(std::string,int,tuple<int,int>,int,
                                                                cv::TermCriteria,bool),
                               6, fileNamePattern, channels, pointsNum, winSize, criteria,withDeriv)
+
+GAPI_TEST_FIXTURE_SPEC_PARAMS(BuildPyr_CalcOptFlow_PipelineTest,
+                              FIXTURE_API(std::string,int,int,bool), 4,
+                              fileNamePattern, winSize, maxLevel, withDerivatives)
+
 } // opencv_test