Merge pull request #15090 from dmatveev:dm/ng-0001-g-api-inference-api

* G-API-NG/API: Introduced inference API and IE-based backend

- Very quick-n-dirty implementation
- OpenCV's own DNN module is not used
- No tests so far

* G-API-NG/IE: Refined IE backend, added more tests

* G-API-NG/IE: Fixed various CI warnings & build issues + tests

- Added tests on multi-dimensional own::Mat
- Added tests on GMatDesc with dimensions
- Documentation on infer.hpp
- Fixed more warnings + added a ROI list test
- Fix descr_of clash for vector<Mat> & standalone mode
- Fix build issue with gcc-4.8x
- Addressed review comments

* G-API-NG/IE: Addressed review comments

- Pass `false` to findDataFile()
- Add deprecation warning suppression macros for IE

modules/gapi/src/executor/gexecutor.cpp

@@ -88,7 +88,7 @@ void cv::gimpl::GExecutor::initResource(const ade::NodeHandle &orig_nh)
     const Data &d = m_gm.metadata(orig_nh).get<Data>();
 
     if (   d.storage != Data::Storage::INTERNAL
-        && d.storage != Data::Storage::CONST)
+        && d.storage != Data::Storage::CONST_VAL)
         return;
 
     // INTERNALS+CONST only! no need to allocate/reset output objects
@@ -105,7 +105,7 @@ void cv::gimpl::GExecutor::initResource(const ade::NodeHandle &orig_nh)
         break;
 
     case GShape::GSCALAR:
-        if (d.storage == Data::Storage::CONST)
+        if (d.storage == Data::Storage::CONST_VAL)
         {
             auto rc = RcDesc{d.rc, d.shape, d.ctor};
             magazine::bindInArg(m_res, rc, m_gm.metadata(orig_nh).get<ConstValue>().arg);