core: add ARM64 NEON support for cvRound in fast_math.hpp

imgcodecs: fix Imgcodecs_Png.write_big test for spng opencv#27589

Close opencv#27588 

### Pull Request Readiness Checklist

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- [x] I agree to contribute to the project under Apache 2 License.
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      Patch to opencv_extra has the same branch name.
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…json_support_backslash

core: support parsing back slash \ in parseKey in FileStorage (JSON) opencv#27587

Fixes opencv#27585 

### 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
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      Patch to opencv_extra has the same branch name.
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…overflow_for_connected_components

Take into account overflow for connected components opencv#27582

### Pull Request Readiness Checklist

Fix opencv#27568 

The problem was caused by a label type overflow (`debug_example.npy` contains `92103` labels, that doesn't fit in the `CV_16U` (`unsigned short`) type). If pass `CV_32S` instead of `CV_16U` as `ltype` - everything will be calculated successfully

Added overflow detection to throw exception with a clear error message instead of strange segfault/assertion error

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

Fixed build with libpng older than 1.5.x and reduced test memory consumption

Jpeg Metadata (iccp and xmp) opencv#27583

### 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
- [ ] 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

to do : 

- [x] consider `m_read_options`
- [x] check if ICCP metadata is suitable to write PNG
- [x] the file `testExifOrientation_3.jpg` used in the test has an ICCP data. this data can be saved in jpg format but could not in PNG and WEBP format. Impovements to check this case with PNGEncoder and WEBPEncoder planned.