Merge pull request #3827 from asmorkalov:as/gapi_migration

Migrate G-API module from main repo to opencv_contrib #3827

Related to https://github.com/opencv/opencv/pull/26469
Required https://github.com/opencv/opencv/pull/26527
CI: https://github.com/opencv/ci-gha-workflow/pull/201

TODO:
- [x]  Python types generator fix
- [x] CI update

### Pull Request Readiness Checklist

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

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the 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

modules/gapi/samples/oak_small_hetero_pipeline.cpp

@@ -0,0 +1,58 @@
+#include <opencv2/gapi.hpp>
+#include <opencv2/gapi/core.hpp>
+#include <opencv2/gapi/cpu/core.hpp>
+#include <opencv2/gapi/gframe.hpp>
+#include <opencv2/gapi/media.hpp>
+
+#include <opencv2/gapi/oak/oak.hpp>
+#include <opencv2/gapi/streaming/format.hpp> // BGR accessor
+
+#include <opencv2/highgui.hpp> // CommandLineParser
+
+const std::string keys =
+    "{ h help  |              | Print this help message }"
+    "{ output  | output.png   | Path to the output file }";
+
+int main(int argc, char *argv[]) {
+    cv::CommandLineParser cmd(argc, argv, keys);
+    if (cmd.has("help")) {
+        cmd.printMessage();
+        return 0;
+    }
+
+    const std::string output_name = cmd.get<std::string>("output");
+
+    std::vector<int> h = {1, 0, -1,
+                          2, 0, -2,
+                          1, 0, -1};
+    std::vector<int> v = { 1,  2,  1,
+                           0,  0,  0,
+                          -1, -2, -1};
+    cv::Mat hk(3, 3, CV_32SC1, h.data());
+    cv::Mat vk(3, 3, CV_32SC1, v.data());
+
+    // Heterogeneous pipeline:
+    // OAK camera -> Sobel -> streaming accessor (CPU)
+    cv::GFrame in;
+    cv::GFrame sobel = cv::gapi::oak::sobelXY(in, hk, vk);
+    // Default camera and then sobel work only with nv12 format
+    cv::GMat out = cv::gapi::streaming::Y(sobel);
+
+    auto args = cv::compile_args(cv::gapi::oak::ColorCameraParams{},
+                                 cv::gapi::oak::kernels());
+
+    auto pipeline = cv::GComputation(cv::GIn(in), cv::GOut(out)).compileStreaming(std::move(args));
+
+    // Graph execution /////////////////////////////////////////////////////////
+    cv::Mat out_mat(1920, 1080, CV_8UC1);
+
+    pipeline.setSource(cv::gapi::wip::make_src<cv::gapi::oak::ColorCamera>());
+    pipeline.start();
+
+    // pull 1 frame
+    pipeline.pull(cv::gout(out_mat));
+
+    cv::imwrite(output_name, out_mat);
+
+    std::cout << "Pipeline finished: " << output_name << " file has been written." << std::endl;
+}