Merge pull request #23691 from dkurt:pycv_float16_fixes

Import and export np.float16 in Python #23691

### Pull Request Readiness Checklist

* Also, fixes `cv::norm` with `NORM_INF` and `CV_16F`

resolves https://github.com/opencv/opencv/issues/23687

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/python/src2/cv2_numpy.cpp

@@ -39,7 +39,7 @@ UMatData* NumpyAllocator::allocate(int dims0, const int* sizes, int type, void*
     int typenum = depth == CV_8U ? NPY_UBYTE : depth == CV_8S ? NPY_BYTE :
     depth == CV_16U ? NPY_USHORT : depth == CV_16S ? NPY_SHORT :
     depth == CV_32S ? NPY_INT : depth == CV_32F ? NPY_FLOAT :
-    depth == CV_64F ? NPY_DOUBLE : f*NPY_ULONGLONG + (f^1)*NPY_UINT;
+    depth == CV_64F ? NPY_DOUBLE : depth == CV_16F ? NPY_HALF : f*NPY_ULONGLONG + (f^1)*NPY_UINT;
     int i, dims = dims0;
     cv::AutoBuffer<npy_intp> _sizes(dims + 1);
     for( i = 0; i < dims; i++ )