Merge pull request #26846 from MaximSmolskiy:fix_bug_with_int64_support_for_FileStorage

Fix bug with int64 support for FileStorage #26846

### Pull Request Readiness Checklist

Fix #26829, https://github.com/opencv/opencv-python/issues/1078

In current implementation of `int64` support raw size of recorded integer is variable (`4` or `8` bytes depending on value). But then we iterate over nodes we need to know it exact value
https://github.com/opencv/opencv/blob/dfad11aae7ef3b3a0643379266bc363b1a9c3d40/modules/core/src/persistence.cpp#L2596-L2609

Bug is that `rawSize` method still return `4` for any integer. I haven't figured out a way how to get variable raw size for integer in this method. I made raw size for integer is constant and equal to `8`.

Yes, after this patch memory consumption for integers will increase, but I don't know a better way to do it yet. At least this fixes bug and implementation becomes more correct

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.cpp

@@ -2441,7 +2441,7 @@ size_t FileNode::rawSize() const
         p += 4;
     size_t sz0 = (size_t)(p - p0);
     if( tp == INT )
-        return sz0 + 4;
+        return sz0 + 8;
     if( tp == REAL )
         return sz0 + 8;
     if( tp == NONE )
@@ -2475,13 +2475,7 @@ void FileNode::setValue( int type, const void* value, int len )
         sz += 4;
 
     if( type == INT )
-    {
-        int64_t ival = *(const int64_t*)value;
-        if (ival > INT_MAX || ival < INT_MIN)
-            sz += 8;
-        else
-            sz += 4;
-    }
+        sz += 8;
     else if( type == REAL )
         sz += 8;
     else if( type == STRING )
@@ -2502,10 +2496,7 @@ void FileNode::setValue( int type, const void* value, int len )
     if( type == INT )
     {
         int64_t ival = *(const int64_t*)value;
-        if (sz > 8)
-            writeInt(p, ival);
-        else
-            writeInt(p, static_cast<int>(ival));
+        writeInt(p, ival);
     }
     else if( type == REAL )
     {