Merge pull request #27246 from gursimarsingh:bug_fix/mcc_dnn_dependency

Fix hard dependency of dnn for mcc module. #27246

Currently building objdetect module without dnn fails due to mcc module. This PR makes the dependency optional, by checking if DNN is available in mcc module. 

### 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
- [x] 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/objdetect/include/opencv2/objdetect/mcc_checker_detector.hpp

@@ -29,7 +29,9 @@
 #ifndef OPENCV_OBJDETECT_MCC_CHECKER_DETECTOR_HPP
 #define OPENCV_OBJDETECT_MCC_CHECKER_DETECTOR_HPP
 #include <opencv2/core.hpp>
+#ifdef HAVE_OPENCV_DNN
 #include <opencv2/dnn.hpp>
+#endif
 #include <opencv2/imgproc.hpp>
 
 //---------------------------------------------------------------
@@ -241,7 +243,9 @@ public:
     *
     */
     CV_WRAP static Ptr<CCheckerDetector> create();
-     /** @brief Set the net which will be used to find the approximate
+
+#ifdef HAVE_OPENCV_DNN
+    /** @brief Set the net which will be used to find the approximate
     *         bounding boxes for the color charts. And returns the implementation of the CCheckerDetector.
     *
     * It is not necessary to use this, but this usually results in
@@ -251,6 +255,7 @@ public:
     *            the function will return false.
     */
     CV_WRAP static Ptr<CCheckerDetector> create(const dnn::Net &net);
+#endif
 
     /** @brief Draws the checker to the given image.
         * @param img image in color space BGR
@@ -280,6 +285,7 @@ public:
 
     CV_WRAP virtual void setColorChartType(ColorChart chartType) = 0;
 
+#ifdef HAVE_OPENCV_DNN
     /** @brief Enables or disables the use of the neural network for detection.
         * @param useDnn Boolean flag to indicate whether to use neural network (true) or not (false).
     */
@@ -287,6 +293,7 @@ public:
     CV_WRAP virtual void setUseDnnModel(bool useDnn) = 0;
 
     CV_WRAP virtual bool getUseDnnModel() const = 0;
+#endif
 
     CV_WRAP virtual const DetectorParametersMCC& getDetectionParams() const = 0;