ts: refactor OpenCV tests

- removed tr1 usage (dropped in C++17)
- moved includes of vector/map/iostream/limits into ts.hpp
- require opencv_test + anonymous namespace (added compile check)
- fixed norm() usage (must be from cvtest::norm for checks) and other conflict functions
- added missing license headers

modules/dnn/test/test_halide_layers.cpp

@@ -10,8 +10,7 @@
 
 #include "test_precomp.hpp"
 
-namespace cvtest
-{
+namespace opencv_test { namespace {
 
 #ifdef HAVE_HALIDE
 using namespace cv;
@@ -712,4 +711,4 @@ TEST(MixedBackends_Halide_Default_Halide, Accuracy)
 }
 #endif  // HAVE_HALIDE
 
-}  // namespace cvtest
+}} // namespace