Merge pull request #18332 from TolyaTalamanov:at/wrap-GIn-GOut

[G-API] Wrap GIn & GOut

* Wrap GIn & GOut into python

* Remove extra brackets

* Use reinterpret_cast

modules/gapi/misc/python/test/test_gapi_core.py

@@ -30,7 +30,7 @@ class gapi_core_test(NewOpenCVTests):
         g_in1 = cv.GMat()
         g_in2 = cv.GMat()
         g_out = cv.gapi.add(g_in1, g_in2)
-        comp = cv.GComputation(g_in1, g_in2, g_out)
+        comp = cv.GComputation(cv.GIn(g_in1, g_in2), cv.GOut(g_out))
 
         for pkg in pkgs:
             actual = comp.apply(in1, in2, args=cv.compile_args(pkg))