Merge pull request #28964 from abhishek-gola:extend_primitive_core_ops

Extended primitive core operations to support new types #28964

The support was already there, this PR tests them on edge cases and patch the fix.

closes: https://github.com/opencv/opencv/issues/24580
### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/core/src/count_non_zero.dispatch.cpp

@@ -198,7 +198,9 @@ void findNonZero(InputArray _src, OutputArray _idx)
         {
             const ushort* ptr16 = (const ushort*)ptr8;
             for( j = 0; j < cols; j++ )
-                if( (ptr16[j]<<1) != 0 ) buf[k++] = j;
+                // mask sign bit so -0 (0x8000) is treated as zero; cannot use <<1 here
+                // because ushort is promoted to int and the sign bit would not be discarded
+                if( (ptr16[j] & 0x7fff) != 0 ) buf[k++] = j;
         }
         else
         {