Merge pull request #26327 from asmorkalov:as/drop_convertFp16

Finally dropped convertFp16 function in favor of cv::Mat::convertTo() #26327 

Partially address https://github.com/opencv/opencv/issues/24909
Related PR to contrib: https://github.com/opencv/opencv_contrib/pull/3812

### 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
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/core/include/opencv2/core.hpp

@@ -492,20 +492,6 @@ For example:
 CV_EXPORTS_W void convertScaleAbs(InputArray src, OutputArray dst,
                                   double alpha = 1, double beta = 0);
 
-/** @brief Converts an array to half precision floating number.
-
-This function converts FP32 (single precision floating point) from/to FP16 (half precision floating point). CV_16S format is used to represent FP16 data.
-There are two use modes (src -> dst): CV_32F -> CV_16S and CV_16S -> CV_32F. The input array has to have type of CV_32F or
-CV_16S to represent the bit depth. If the input array is neither of them, the function will raise an error.
-The format of half precision floating point is defined in IEEE 754-2008.
-
-@param src input array.
-@param dst output array.
-
-@deprecated Use Mat::convertTo with CV_16F instead.
-*/
-CV_EXPORTS_W void convertFp16(InputArray src, OutputArray dst);
-
 /** @brief Performs a look-up table transform of an array.
 
 The function LUT fills the output array with values from the look-up table. Indices of the entries

modules/core/include/opencv2/core/cuda.hpp

@@ -1324,7 +1324,7 @@ CV_EXPORTS_W void printShortCudaDeviceInfo(int device);
 @param _src input array.
 @param _dst output array.
 @param stream Stream for the asynchronous version.
-@sa convertFp16
+@sa cv::Mat::convertTo
 */
 CV_EXPORTS void convertFp16(InputArray _src, OutputArray _dst, Stream& stream = Stream::Null());