Merge pull request #21107 from take1014:remove_assert_21038

resolves #21038

* remove C assert

* revert C header

* fix several points in review

* fix test_ds.cpp

modules/features2d/test/test_descriptors_regression.cpp

@@ -159,7 +159,7 @@ protected:
 
     void emptyDataTest()
     {
-        assert( dextractor );
+        CV_Assert( dextractor );
 
         // One image.
         Mat image;
@@ -205,7 +205,7 @@ protected:
 
     void regressionTest()
     {
-        assert( dextractor );
+        CV_Assert( dextractor );
 
         // Read the test image.
         string imgFilename =  string(ts->get_data_path()) + FEATURES2D_DIR + "/" + IMAGE_FILENAME;