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_nms.cpp

@@ -7,8 +7,7 @@
 
 #include "test_precomp.hpp"
 
-namespace cvtest
-{
+namespace opencv_test { namespace {
 
 TEST(NMS, Accuracy)
 {
@@ -38,4 +37,4 @@ TEST(NMS, Accuracy)
         ASSERT_EQ(indices[i], ref_indices[i]);
 }
 
-}//cvtest
+}} // namespace