Added some helper function in 'mcc'

[AjitPant]

Earlier the CChecker class only stores the four corners of the chart, others were to be calculated by the user using perspective transform. Now the centers of each squares in the chart, along with a crop of their center is stored, also the loss per patch is also stored, which can be used by user. Also removed some code duplication in transform_points_forward.

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 OpenCV (BSD) License.
• [ X ] To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
• [x] The PR is proposed to proper branch
• [ ] There is reference to 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