Merge pull request #27833 from asmorkalov:as/move_gen_pattern

Moved pattern generator to apps and rewrote tutorial #27833

### Pull Request Readiness Checklist

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

- [x] I agree to contribute to the project under Apache 2 License.
- [x] 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

modules/calib3d/include/opencv2/calib3d.hpp

@@ -1385,7 +1385,7 @@ the board to make the detection more robust in various environments. Otherwise,
 border and the background is dark, the outer black squares cannot be segmented properly and so the
 square grouping and ordering algorithm fails.
 
-Use the `gen_pattern.py` Python script (@ref tutorial_camera_calibration_pattern)
+Use the `generate_pattern.py` Python script (@ref tutorial_camera_calibration_pattern)
 to create the desired checkerboard pattern.
  */
 CV_EXPORTS_W bool findChessboardCorners( InputArray image, Size patternSize, OutputArray corners,
@@ -1444,7 +1444,7 @@ which are located on the outside of the board. The following figure illustrates
 a sample checkerboard optimized for the detection. However, any other checkerboard
 can be used as well.
 
-Use the `gen_pattern.py` Python script (@ref tutorial_camera_calibration_pattern)
+Use the `generate_pattern.py` Python script (@ref tutorial_camera_calibration_pattern)
 to create the corresponding checkerboard pattern:
 \image html pics/checkerboard_radon.png width=60%
  */