Add KV cache with paged attention and prefetch #29127
Closes: https://github.com/opencv/opencv/issues/27159
### 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
- [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
Add Qwen2.5 tokenizer support for dnn #28781
OpenCV extra: https://github.com/opencv/opencv_extra/pull/1334
Extended the dnn tokenizer support to qwen2.5 tokenization.
- Add QWEN2_5 pre-tokenizer regex pattern to utils.hpp
- Generalised buildTokenizerGPT to buildTokenizerFromJson to handle gpt2/gpt4/ and qwen2.5
- Add qwen2/qwen2.5 model type support with special token handling
- Add Qwen2.5 tests
- Add end-to-end qwen_inference script for Qwen2.5 ONNX model
### 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
- [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
Prasad Ayush Kumar
Varun Jaiswal