Add ocl version BackgroundSubtractorKNN (#10553)

* Add ocl version bgfg_knn

* Add ocl KNN perf test

* ocl KNN: Avoid unnecessary initializing when non-UMat parameters are used

* video: turn off OpenCL for color KNN on Intel devices

due performance degradation

* video: turn off KNN OpenCL on Apple devices with Intel iGPU

due process freeze during clBuildProgram() call

Fix OpenCL's wrong output of calcOpticalFlowPyrLK function's output vector of err. Improve err's precison of the calcOpticalFlowPyrLK OpenCL function and add the relative test.

It could reduce 7 multiplications every iteration.
Signed-off-by: Yan Wang <yan.wang@linux.intel.com>

1. Remove uncessary index calculation.
2. Use mad/mad24 as possible.
Signed-off-by: Yan Wang <yan.wang@linux.intel.com>

1. decrease branch number in CL code by replacing them into weights
2. decrease local mem pressure in reduce operation by using private variables
3. decrease image sampler pressure by caching data into local memory
4. remove unnecessary sync point on the HOST side.

fix for cv::LUT and cv::transpose