G-API: Unification of own:: structures with cv:: (Size, Point, Rect)

* deowned Size Rect Point

* Deownded Size Rect Point

* With Scalar

- control using of clEnqueueMapBuffer or clEnqueueReadBuffer[Rect]
- added benchmarks with OpenCL buffer access use cases

G-API: Unification of own:: Scalar with cv:: Scalar

* cvdefs.hpp

* Small changes

* Deowned Scalar. Does't work

* Something

* Removed to_ocv for Scalar

* Clear code

* Deleted whitespaces

* Added include<..own/scalar.hpp in cvdefs.hpp.

* Long string split on two now

* Comment about scalar

* Comment about crutch

* Removed second varible in scalar_wrapper

* Changed wrapper for scalar, alignment

* Alignment

* Whitespaces

* Removed scalar_wrapper

backporting commit 99436bb8