Merge pull request #27453 from MELSunny:4.x

Add Raspberry Pi 4 and 5 V4L2 Stateless HEVC Hardware Acceleration with FFmpeg #27453

This PR enables V4L2 stateless HEVC hardware acceleration for Raspberry Pi 5 within OpenCV's videoio module. It leverages FFmpeg's drm acceleration ([FFmpeg API changes](ee1f79b0fa/doc/APIchanges (L1529))), significantly improving HEVC decoding performance on RPi5 for robotics and embedded vision applications.

I have a working proof-of-concept with local benchmarks showing clear gains.

Checklist Status:

Ready: License, branch (4.x), FFmpeg reference, and (linked) related issue (#27452).
Seeking Guidance: Need help with formal C++ performance/accuracy tests, opencv_extra integration, and full documentation/examples.
As a Python developer, I welcome C++ best practice feedback and assistance with testing setup.

### 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
- [ ] 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

samples/tapi/video_acceleration.cpp

@@ -42,6 +42,7 @@ struct {
     { VIDEO_ACCELERATION_D3D11, "d3d11" },
     { VIDEO_ACCELERATION_VAAPI, "vaapi" },
     { VIDEO_ACCELERATION_MFX, "mfx" },
+    { VIDEO_ACCELERATION_DRM, "drm" },
 };
 
 class FPSCounter {