G-API planar kernels (#14917)

* Added resizeP with tests

* NV12 planar filters

* fix warnings in ResizeP test

* fix out mat ocv warning

* sz_on - > sz rename

* cpu tests new signature

* try to fix resizeP test

* trailing spaces remove

* doxygen doc fixed

* doxygen minor fix

* more doxygen fixes

* Doxygen corrected and extended after review.