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/onevpl_source_to_bgr_conv.cpp

@@ -0,0 +1,106 @@
+#include <algorithm>
+#include <fstream>
+#include <iostream>
+#include <cctype>
+#include <tuple>
+#include <memory>
+
+#include <opencv2/imgproc.hpp>
+#include <opencv2/gapi.hpp>
+#include <opencv2/gapi/core.hpp>
+#include <opencv2/gapi/gpu/ggpukernel.hpp>
+#include <opencv2/gapi/streaming/onevpl/source.hpp>
+#include <opencv2/gapi/streaming/onevpl/data_provider_interface.hpp>
+#include <opencv2/gapi/streaming/onevpl/default.hpp>
+#include <opencv2/highgui.hpp> // CommandLineParser
+#include <opencv2/gapi/ocl/core.hpp>
+
+const std::string about =
+    "This is an example presents decoding on GPU using VPL Source and passing it to OpenCL backend";
+const std::string keys =
+    "{ h help       |                                                                | Print this help message }"
+    "{ input        |                                                                | Path to the input video file. Use .avi extension }"
+    "{ accel_mode   | mfxImplDescription.AccelerationMode:MFX_ACCEL_MODE_VIA_D3D11   | Acceleration mode for VPL }";
+
+namespace {
+namespace cfg {
+// FIXME: Move OneVPL arguments parser to a single place
+typename cv::gapi::wip::onevpl::CfgParam create_from_string(const std::string &line);
+} // namespace cfg
+} // anonymous namespace
+
+int main(int argc, char *argv[]) {
+    cv::CommandLineParser cmd(argc, argv, keys);
+    cmd.about(about);
+    if (cmd.has("help")) {
+        cmd.printMessage();
+        return 0;
+    }
+
+    // Get file name
+    const auto input = cmd.get<std::string>("input");
+    const auto accel_mode = cmd.get<std::string>("accel_mode");
+
+    // Create VPL config
+    std::vector<cv::gapi::wip::onevpl::CfgParam> source_cfgs;
+    source_cfgs.push_back(cfg::create_from_string(accel_mode));
+
+    // Create VPL-based source
+    std::shared_ptr<cv::gapi::wip::onevpl::IDeviceSelector> default_device_selector =
+                                                cv::gapi::wip::onevpl::getDefaultDeviceSelector(source_cfgs);
+
+    cv::gapi::wip::IStreamSource::Ptr source = cv::gapi::wip::make_onevpl_src(input, source_cfgs,
+                                                                              default_device_selector);
+
+    // Build the graph
+    cv::GFrame in; // input frame from VPL source
+    auto bgr_gmat = cv::gapi::streaming::BGR(in); // conversion from VPL source frame to BGR UMat
+    auto out = cv::gapi::blur(bgr_gmat, cv::Size(4,4)); // ocl kernel of blur operation
+
+    cv::GStreamingCompiled pipeline = cv::GComputation(cv::GIn(in), cv::GOut(out))
+        .compileStreaming(cv::compile_args(cv::gapi::core::ocl::kernels()));
+    pipeline.setSource(std::move(source));
+
+    // The execution part
+    size_t frames = 0u;
+    cv::TickMeter tm;
+    cv::Mat outMat;
+
+    pipeline.start();
+    tm.start();
+
+    while (pipeline.pull(cv::gout(outMat))) {
+        cv::imshow("OutVideo", outMat);
+        cv::waitKey(1);
+        ++frames;
+    }
+    tm.stop();
+    std::cout << "Processed " << frames << " frames" << " (" << frames / tm.getTimeSec() << " FPS)" << std::endl;
+
+    return 0;
+}
+
+namespace {
+namespace cfg {
+typename cv::gapi::wip::onevpl::CfgParam create_from_string(const std::string &line) {
+    using namespace cv::gapi::wip;
+
+    if (line.empty()) {
+        throw std::runtime_error("Cannot parse CfgParam from emply line");
+    }
+
+    std::string::size_type name_endline_pos = line.find(':');
+    if (name_endline_pos == std::string::npos) {
+        throw std::runtime_error("Cannot parse CfgParam from: " + line +
+                                 "\nExpected separator \":\"");
+    }
+
+    std::string name = line.substr(0, name_endline_pos);
+    std::string value = line.substr(name_endline_pos + 1);
+
+    return cv::gapi::wip::onevpl::CfgParam::create(name, value,
+                                                   /* vpp params strongly optional */
+                                                   name.find("vpp.") == std::string::npos);
+}
+} // namespace cfg
+} // anonymous namespace