GAPI (fluid): RGB to YUV optimization (#13174)

* GAPI (fluid): RGB to YUV: activate performance tests

* GAPI (fluid): speedup 4-8x RGB-to-YUV, 2.5x YUV to RGB with int16 arithmetic

* GAPI (fluid): RGB <--> YUV: fixed compiler warning

* GAPI (fluid): RGB <--> YUV: additional speedup 2-3x times (10-15x over original) via manual CV_SIMD

* GAPI (fluid): RGB <--> YUV: dynamic CV_SIMD dispatching