Merge pull request #18196 from mpashchenkov:mp/garray-initialization

[G-API]: Add GArray initialization support

* Added GArray initialization (CONST_VALUE, GScalar analog) and test for this

* Whitespaces

* And one more space

* Trailing whitespace

* Test name changed. Build with magic commands.

* GArray works with rvalue initialization

* Code cleanup

* Ternary operator in the initialization list.

modules/gapi/src/api/gproto.cpp

@@ -79,6 +79,7 @@ cv::GRunArg cv::value_of(const cv::GOrigin &origin)
     switch (origin.shape)
     {
     case GShape::GSCALAR: return GRunArg(util::get<cv::Scalar>(origin.value));
+    case GShape::GARRAY:  return GRunArg(util::get<cv::detail::VectorRef>(origin.value));
     default: util::throw_error(std::logic_error("Unsupported shape for constant"));
     }
 }