Change iteration to iterate separately when the video is decode on a GPU to account for different number of frames

- don't use TBB in samples

Also these samples require TBB, so they are not tested during default OpenCV builds

Regular OpenCV perf tests should be used instead

- Recommended compiler checks:
  - GCC: CV_GCC
  - Clang: CV_CLANG
- fixed problem with CMAKE_CXX_COMPILER_ID=Clang/AppleClang mess on MacOSX
  Details: cmake --help-policy CMP0025
- do not declare Clang as GCC compiler

- allow installing samples sources on all platforms
  even if BUILD_EXAMPLES is disabled,  fixed minor
  issues in sources installation process
- use 'example_<group>_<name>' scheme for target and binary file naming
- use single function for sample executable creation

Found via `codespell -q 3 --skip="./3rdparty" -I ../opencv-whitelist.txt`

- removed tr1 usage (dropped in C++17)
- moved includes of vector/map/iostream/limits into ts.hpp
- require opencv_test + anonymous namespace (added compile check)
- fixed norm() usage (must be from cvtest::norm for checks) and other conflict functions
- added missing license headers

* Remove "simple" flow estimation from help (because it was disabled by 653bca8b)
* Add `flush` after printing iteration number for better UX

compute() for BP and CSBP output 32-bit floating-point mat, and in cv::imshow() 32-bit floating-point is recognized as [0,1] and maped to [0,255], that causes gray window for BP and CSBP.

Original commit is a5f19f7dd6ae5bc93f73e0417a9e0bfd34c01672

in this case the sample will not be built if OpenGL is not found

(cherry picked from commit ff002203)

As is it was not possible to use CUDA.