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

Overview

The goal of this PR is to support all different overloads for compileStreaming method in python, such as:

• compileStreaming(cv::GMetaArgs, cv::GCompileArgs = { })
• compileStreaming(cv::ExtractMetaCallback, cv::GCompileArgs = { })
• compileStreaming(cv::GCompileArgs = { })

To wrap these methods need to add GAPI_WRAP macros before every signature. The generated code will try every overloads in order from top to bottom as declared in c++ file and if overload isn't suitable (pyopencv_to for params return false) try the next one. So the problem was that pyopencv_to(cv::ExtractMetaCallback) always return true which means that the compileStreaming(cv::ExtractMetaCallback, cv::GCompileArgs = { }) is always suitable.
So the possible solution for that problem is put this overload in the end in that case it will be chosen only if others aren't suitable.

• Added queue_capacity compile arg in order to test overloads.
• Implemented pyopencv_to(cv::GMetaArg) in order to wrap compileStreaming(cv::GMetaArgs, cv::GCompileArgs)

Build configuration

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-2021.3.0:20.04
build_image:Custom Win=openvino-2021.2.0
build_image:Custom Mac=openvino-2021.2.0

test_modules:Custom=gapi,python2,python3,java
test_modules:Custom Win=gapi,python2,python3,java
test_modules:Custom Mac=gapi,python2,python3,java

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