Merge pull request #26872 from sturkmen72:ImageEncoders_revisions

Performance tests for image encoders and decoders and code cleanup #26872

### 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

modules/imgcodecs/src/grfmt_gif.cpp

@@ -514,19 +514,11 @@ GifEncoder::~GifEncoder() {
     close();
 }
 
-bool GifEncoder::isFormatSupported(int depth) const {
-    return depth == CV_8U;
-}
-
-bool GifEncoder::write(const Mat &img, const std::vector<int> &params) {
-    std::vector<Mat> img_vec(1, img);
-    return writemulti(img_vec, params);
-}
-
 bool GifEncoder::writeanimation(const Animation& animation, const std::vector<int>& params) {
     if (animation.frames.empty()) {
         return false;
     }
+    CV_CheckDepthEQ(animation.frames[0].depth(), CV_8U, "GIF encoder supports only 8-bit unsigned images");
 
     if (m_buf) {
         if (!strm.open(*m_buf)) {