G-API: Fix various issues for 4.2 release

* G-API: Fix issues reported by Coverity

- Fixed: passing values by value instead of passing by reference

* G-API: Fix redundant std::move()'s in return statements

Fixes #15903

* G-API: Added a smarter handling of Stop messages in the pipeline

- This should fix the "expected 100, got 99 frames" problem
- Fixes #15882

* G-API: Pass enum instead of GKernelPackage in Streaming test parameters

- Likely fixes #15836

* G-API: Address review issues in new bugfix comments

* G-API-NG/Docs: Added a tutorial page on interactive face detection sample

- Introduced a "--ser" option to run the pipeline serially for
  benchmarking purposes
- Reorganized sample code to better fit the documentation;
- Fixed a couple of issues (mainly typos) in the public headers

* G-API-NG/Docs: Reflected meta-less compilation in new G-API tutorial

* G-API-NG/Docs: Addressed review comments on Face Analytics Pipeline example

add CropAndResize layer for CUDA backend

* add CropAndResize layer

* process multiple channels per iteration

cuda4dnn(resize): process multiple channels each iteration

* resize bilinear: process multiple chans. per iter.

* remove unused headers

* correct dispatch logic

* resize_nn: process multiple chans. per iter.

* G-API: Addressed various documentation issues

- Fixed various typos and missing references;
- Added brief documentaion on G_TYPED_KERNEL and G_COMPOUND_KERNEL macros;
- Briefly described GComputationT<>;
- Briefly described G-API data objects (in a group section).

* G-API: Some clean-ups in doxygen, also a chapter on Render API

* G-API: Expose more graph compilation arguments in the documentation

* G-API: Address documentation review comments

- Now user doesn't need to do `combine(x, combine(y, combine(z, zz)))` but
  just `combine(x, y, z, zz)`

* calib3d: use normalized input in solvePnPGeneric()

* calib3d: java regression test for solvePnPGeneric

* calib3d: python regression test for solvePnPGeneric

* core: disable invalid constructors in C API by default

- C API objects will lose their default initializers through constructors

* samples: stop using of C API

Fix cudacodec python

* Add python bindings to cudacodec.

* Allow args with CV_OUT GpuMat& or CV_OUT cuda::GpuMat& to generate python bindings that allow the argument to be an optional output in the same way as OutputArray.

* Add wrapper flag to indicate that an OutputArray is a GpuMat.

* python: drop CV_GPU, extra checks in test

* Remove "cuda::GpuMat" check rom python parser

- #if 0
- #ifdef __OPENCV_BUILD

- required to unregister callbacks from system

G-API-NG/Streaming: don't require explicit metadata in compileStreaming()

* First probably working version
Hardcode gose to setSource() :)

* Pre final version of move metadata declaration from compileStreaming() to setSource().

* G-API-NG/Streaming: recovered the existing Streaming functionality

- The auto-meta test is disabling since it crashes.
- Restored .gitignore

* G-API-NG/Streaming: Made the meta-less compileStreaming() work

- Works fine even with OpenCV backend;
- Fluid doesn't support such kind of compilation so far - to be fixed

* G-API-NG/Streaming: Fix Fluid to support meta-less compilation

- Introduced a notion of metadata-sensitive passes and slightly
  refactored GCompiler and GFluidBackend to support that
- Fixed a TwoVideoSourcesFail test on streaming

* Add three smoke streaming tests to gapi_streaming_tests.
All three teste run pipeline with two different input sets
1) SmokeTest_Two_Const_Mats test run pipeline with two const Mats
2) SmokeTest_One_Video_One_Const_Scalar test run pipleline with Mat(video source) and const Scalar
3) SmokeTest_One_Video_One_Const_Vector test run pipeline with Mat(video source) and const Vector
 # Please enter the commit message for your changes. Lines starting

* style fix

* Some review stuff

* Some review stuff