Merge pull request #27113 from sturkmen72:spng-CV_16U

Fixing imread() function 16 bit reading png problem with libspng #27113

The purpose of the PR was to load bit-exact compatible results with libspng and libpng. To test this, `Imgcodecs_Png_PngSuite `was improved. Files containing gamma correction were moved to a separate test called `Imgcodecs_Png_PngSuite_Gamma `because the logic created for the other files did not apply to those with gamma correction. As a result, libspng now works in bit-exact compatibility with libpng. The code can be refactored later.

### Pull Request Readiness Checklist

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- [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
- [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.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/imgcodecs/misc/java/test/ImgcodecsTest.java

@@ -15,6 +15,10 @@ import java.util.List;
 public class ImgcodecsTest extends OpenCVTestCase {
 
     public void testAnimation() {
+        if (!Imgcodecs.haveImageWriter("*.apng")) {
+           return;
+        }
+
         Mat src = Imgcodecs.imread(OpenCVTestRunner.LENA_PATH, Imgcodecs.IMREAD_REDUCED_COLOR_4);
         assertFalse(src.empty());