Manually add typing stubs for functions defined in cv2_highgui.hpp:

• createTrackbar

   def createTrackbar(trackbarName: str,
                 windowName: str,
                 value: int,
                 count: int,
                 onChange: Callable[[int], None]) -> None: ...

• createButton

  def createButton(buttonName: str,
                   onChange: Callable[[tuple[int] | tuple[int, Any]], None],
                   userData: Any | None = ...,
                   buttonType: int = ...,
                   initialButtonState: int = ...) -> None: ...

• setMouseCallback

  def setMouseCallback(
      windowName: str,
      onMouse: Callback[[int, int, int, int, Any | None], None],
      param: Any | None = ...
  ) -> None: ...

closes opencv/opencv-python#875

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake