G-API aux kernels (#14599)

* Removed gcpuimgproc.hpp and gcpucore.hpp

* Changed GModel::orderedInputs and orderedOutputs to get ConstGraph&

* Added auxiliaryKernels() method of GBackend::Priv

G-API: own::Mat as output computation doesn't work (#14151)

* Fix bug with output own::Mat

* Fix comments to review

* Fix preprocess condition

* Fix comments to review

G-API: GComputation doesn't work with output vector<cv::Mat> (#14150)

* Fix bug with gcomputation output vector

* Add test fixture

* Fix comments to review

* Fix alignment

G-API: Kernel package design (#13851)

* Remove cv::unite_policy from API

* Add check that all id in kernel package are unique

* Refactor checker id procedure

* Remove cv::gapi::GLookupOrder from API

* Implement cv::gapi::use_only

* Fix samples

* Fix docs

* Fix comments to review

* Remove unite_policy

* Fix GKernelPackage::backends()

* Fix comments to review

* Fix all_unique

* Fix comments to review

* Fix comments to review

* Remove out of date tests

Lab, Luv and XYZ conversions rewritten to wide intrinsics (#14106)

* rgb2xyz<float> re-vectorized

* rgb2xyz_i vectorized for ushort and uchar

* xyz2rgb<float> vectorized

* xyz2rgb_i vectorized for both uchar and ushort

* intermediate conversions (int->float) rewritten

* packed rgb2luv rewritten

* (some) float conversions rewritten

* burnt volatile int _3 and similar

* RGB2Lab_b rewritten

* tests: logging made better

* RGB2Lab_f (LRGB path) rewritten

* Lab2RGBfloat rewritten

* Lab2RGBinteger and Lab2RGB_b rewritten to wide universal intrinsics

* Luv2RGBinteger wide vectorized

* RGB2Lab_b fixed: v_sub_wrap instead of saturated sub

* warnings fixed

* trying to fix compilation on older compilers

* using 16x8 registers for 8-element dot product

* cleanup added

* splineInterpolate: loop unrolled, perf fix for f32x4

* Lab2RGBfloat: grab 2x more data to process on f32x4

* nrepeats for Luv2RGBfloat, +20% perf

* minor

* nrepeats to RGB2Lab_f

* Lab2RGBinteger: no tab for linear BGR

* nrepeats for RGB2Luvfloat

* Luv2RGBinteger: no tab for linear RGB

* +10% more to perf of Luv2RGBfloat

* nrepeats for 256-simd for Lab2RGBfloat

* less warnings

* BOM removed

* CV_SIMD_WIDTH used for lanes number checking

* trilinearPackedInterpolate: 128-bit specialization added

* fix build; no vx_cleanup(), instrumentation instead

* added support for Eigen cross-compilation

* cmake: fix Eigen detection

Fix wrong indentation as well while at it

Add SOLVEPNP_IPPE for planar pose estimation. Add solvePnPGeneric function that returns all the pose solutions and the reprojection errors.