patch dataset `transform` should be applied to the patches only

[wyli]

Describe the bug

import monai
from monai.transforms import DataStatsd
import numpy as np

img = [{"img": np.zeros((1, 30, 40, 3))}]
patch_func = monai.data.PatchIterd(keys=["img"], patch_size=(30, 40, 1))
transform = DataStatsd(keys=["img"])

for x in monai.data.GridPatchDataset(img, patch_iter=patch_func, transform=transform):
    print(x[0]["img"].shape)

should generate slices in shape (30, 40, 1),
but the transform is mistakenly applied in the base class:

Data statistics:
Type: <class 'numpy.ndarray'> float64
Shape: (1, 30, 40, 3)
Value range: (0.0, 0.0)
Data statistics:
Type: <class 'numpy.ndarray'> float64
Shape: (1, 30, 40, 1)
Value range: (0.0, 0.0)
(1, 30, 40, 1)
Data statistics:
Type: <class 'numpy.ndarray'> float64
Shape: (1, 30, 40, 1)
Value range: (0.0, 0.0)
(1, 30, 40, 1)
Data statistics:
Type: <class 'numpy.ndarray'> float64
Shape: (1, 30, 40, 1)
Value range: (0.0, 0.0)
(1, 30, 40, 1)

Expected behavior
the super().__iter__() shouldn't trigger the patch transform

MONAI/monai/data/grid_dataset.py

Line 194 in 7504526

for image in super().__iter__():