[G-API] Adding GMat operators to the standalone mode

[anton-potapov]

Current stand-alone mode miss GMat operators (e.g. like / or +).

This patch address this shortcoming.

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
• The PR is proposed to proper branch
• There is reference to original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake

Xforce_builders_only=linux,docs
force_builders=Custom,Custom Win,Custom Mac
build_gapi_standalone:Linux x64=ade-0.1.1f
build_gapi_standalone:Win64=ade-0.1.1f
build_gapi_standalone:Mac=ade-0.1.1f
build_gapi_standalone:Linux x64 Debug=ade-0.1.1f

Xbuild_image:Custom=centos:7
Xbuildworker:Custom=linux-1
build_gapi_standalone:Custom=ade-0.1.1f

build_image:Custom=ubuntu-openvino-2020.3.0:16.04
build_image:Custom Win=openvino-2020.3.0
build_image:Custom Mac=openvino-2020.3.0

test_modules:Custom=gapi
test_modules:Custom Win=gapi
test_modules:Custom Mac=gapi

buildworker:Custom=linux-1
# disabled due high memory usage: test_opencl:Custom=ON
test_opencl:Custom=OFF
test_bigdata:Custom=1
test_filter:Custom=*

[dmatveev]

Please don't put me to reviews by default.

[dmatveev]

I don't support change like this, / and - may be defined locally for the preprocessing case, no need to bring this into the mainline.

[dmatveev]

It bloats our standalone build .a file. Can you please measure the size before/after?

Also -- not sure if kernels_core will work in the standalone mode at all - since the dispatch thing is different when it is used in the IE preproc.

[asenyaev]

jenkins cn please retry a build

[dmatveev]

@anton-potapov (cc: @anna-khakimova ) - is this PR still required or not? I believe it is related to the mean-value part of the OpenVINO preprocessing, but the latter somehow works without this

[asmorkalov]

Closed by dmatveev request.