[GSOC 2025] PNG&WebP Metadata Reading Writing Improvements #27503
Merge with https://github.com/opencv/opencv_extra/pull/1271
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APNG encoding optimization #26849
related #26840
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Fix potential READ memory access #26782
This fixes https://oss-fuzz.com/testcase-detail/4923671881252864 and https://oss-fuzz.com/testcase-detail/5048650127966208
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Add more boundary checks. #26739
Also fix a bug in read_chunk where we could end up with png_get_uint_32(len) + 12 < 4
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Fix leaks in cv::PngDecoder #26701
Bug: oss-fuzz:386688709
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Animated PNG Support #25715
Continues https://github.com/opencv/opencv/pull/25608
### Pull Request Readiness Checklist
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Suleyman TURKMEN
Vincent Rabaud
Alexander Alekhin
vbystricky