Merge pull request #28664 from pratham-mcw:armpl_dft_opt

Add ARMPL support for DFT Function #28664

- This PR introduces hal/armpl/ with implementation of 1D, 2D DFT and DCT routines using ARM Performance Libraries as a custom HAL replacement for OpenCV's DFT & DCT Function.
- ArmPL MSI package is automatically downloaded and extracted via CMake when building on Windows ARM64, with a WITH_ARMPL option that defaults to ON for that platform.
- Forward and inverse real DFT calls in dxt.cpp are routed through ArmPL when available, with scaling applied only when needed.
- Test error thresholds in test_dxt.cpp are relaxed (from 1e-5 to 2e-4 for float ) to account for numerical differences between ArmPL and OpenCV's reference DFT results.

**Performance Benchmarks :**
<img width="993" height="835" alt="image" src="https://github.com/user-attachments/assets/76def647-6d20-4bce-8bc9-7363e723669f" />

- [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

cmake/OpenCVFindLibsPerf.cmake

@@ -38,6 +38,21 @@ if(WITH_IPP)
   endif()
 endif()
 
+if(WITH_ARMPL)
+  include("${OpenCV_SOURCE_DIR}/cmake/OpenCVFindARMPL.cmake")
+  if(HAVE_ARMPL)
+    message(STATUS "Using ARM Performance Libraries")
+    ocv_include_directories(${ARMPL_INCLUDE_DIRS})
+    list(APPEND OPENCV_LINKER_LIBS ${ARMPL_LIBRARIES})
+    add_compile_definitions(HAVE_ARMPL)
+    if(WITH_OPENMP AND OpenMP_CXX_FOUND)
+      list(APPEND OPENCV_LINKER_LIBS OpenMP::OpenMP_CXX)
+    endif()
+  else()
+    message(STATUS "ARM Performance Libraries: Not found or not available")
+  endif()
+endif()
+
 # --- CUDA ---
 if(WITH_CUDA)
   if(ENABLE_CUDA_FIRST_CLASS_LANGUAGE)