Add perf test for popular models

[varun-jaiswal17]

requires (YOLO26n , RetinaFace model download) : opencv/opencv_extra#1357

added performance tests for 14 modern deep learning models to modules/dnn/perf/perf_net.cpp.

Tests added

• RT_DETR_L
• RF_DETR
• Grounding_DINO
• BlazeFace
• RetinaFace
• YOLO26n
• YOLO26m_Seg
• SegFormer_B2_Clothes
• Depth_Anything_V2
• SigLIP
• OWLv2
• RAFT
• SAM2_Encoder
• SAM2_Decoder

Models are available at: https://drive.google.com/drive/folders/1lpYAWSLMtxcmfDtYjiw0qwzZX0bCH-i4

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• 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
• 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

[asmorkalov]

Generic comments about the PR:

1. Please replace the URLs with the original urls, where it's possible.
2. It makes sense to enable the tests by default. For now the tests are guarded by CV_TEST_TAG_DEBUG_LONG and the tests are not executed by default and in CI.

[asmorkalov]

BlaseFace model was added with block layout support PR #28839

[asmorkalov]

@varun-jaiswal17 Please rebase and fix conflicts.