G-API: Add output allocation tests for backends (#15012)

* Add output tests for backends

* Fix large size test: output is in fact reallocated

* Use cv::Mat copies for reallocation tracking

* Separate LargeSizeWithCorrectSubmatrix test

* Rename backed output allocation tests

* Address code review feedback

Update test names

Add illustrative "expect (non-)empty" checks

Rename mat "copy" to mat reference

Add more pointer checks

* Add illustrative checks

G-API: clean up accuracy tests (#14945)

* Delete createOutputMatrices flag

Update the way compile args function is created

Fix instantiation suffix print function

* Update comment (NB)

* Make printable comparison functions

* Use defines instead of objects for compile args

* Remove custom printers, use operator<< overload

* Remove SAME_TYPE and use -1 instead

* Delete createOutputMatrices flag in new tests

* Fix GetParam() printed values

* Update Resize tests: use CompareF object

* Address code review feedback

* Add default cases for operator<< overloads

* change throw to GAPI_Assert

avoid generation of copy ctors with unique_ptr members

…aster

 - added ability to use custom implementation of "parallel for" function

…t handling

…ism_custom_pfor

…work

G-API: GAPI_TRANSFORM internal functionality rework (#14952)

* Change internal pattern and substitute signatures and refactor tests

* Enhance GArrayU with type-checker function

Add a couple of new tests on GAPI_TRANSFORM

* G-API: fix GOCLExecutable issue with UMat lifetime

Add tests on initialized/uninitialized outputs for all
backends

* Use proper clean-up procedure for magazine

* Rename InitOut test and reduce tested sizes

* Enable output allocation test

OpenCV 4.1.1

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

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

* 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

…check

…bilinear

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.

add CropAndResize layer for CUDA backend

* add CropAndResize layer

* process multiple channels per iteration

…face_detection

* 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

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

…nto fix_voronoi_typo

# Conflicts:
#	doc/tutorials/dnn/dnn_android/dnn_android.markdown
#	doc/tutorials/introduction/cross_referencing/tutorial_cross_referencing.markdown
#	modules/core/include/opencv2/core/version.hpp
#	modules/dnn/src/layers/elementwise_layers.cpp
#	modules/python/package/setup.py
#	platforms/android/build_sdk.py
#	platforms/android/service/engine/AndroidManifest.xml
#	platforms/android/service/engine/src/org/opencv/engine/OpenCVEngineService.java
#	platforms/android/service/readme.txt
#	platforms/maven/opencv-it/pom.xml
#	platforms/maven/opencv/pom.xml
#	platforms/maven/pom.xml