Merge pull request #26871 from MaximSmolskiy:fix-filestorage_io_test-test_base64-for-64-bit-integer-types

Support 64-bit integer types for FileStorage Base64 #26871

### Pull Request Readiness Checklist

Related to https://github.com/opencv/opencv/pull/26846#issuecomment-2618159277
OpenCV extra: https://github.com/opencv/opencv_extra/pull/1232

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
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/core/src/persistence_base64_encoding.cpp

@@ -208,6 +208,8 @@ int base64::icvCalcStructSize(const char *dt, int initial_size) {
             case 'i': { elem_max_size = std::max( elem_max_size, sizeof(int   ) ); break; }
             case 'f': { elem_max_size = std::max( elem_max_size, sizeof(float ) ); break; }
             case 'd': { elem_max_size = std::max( elem_max_size, sizeof(double) ); break; }
+            case 'I': { elem_max_size = std::max( elem_max_size, sizeof(int64_t)); break; }
+            case 'U': { elem_max_size = std::max( elem_max_size, sizeof(uint64_t)); break; }
             default: break;
         }
     }
@@ -347,6 +349,11 @@ size_t base64::RawDataToBinaryConvertor::make_to_binary_funcs(const std::string
                     size = sizeof(double);
                     pack.func = to_binary<double>;
                     break;
+                case 'I':
+                case 'U':
+                    size = sizeof(uint64_t);
+                    pack.func = to_binary<uint64_t>;
+                    break;
                 case 'r':
                 default:
                     CV_Error(cv::Error::StsError, "type is not supported");