Incorrect ImageMobject Content

### Describe the bug
When I create a large number of ImageMobjects, some of them get incorrectly set to another ImageMobject's image. There should be 35 green checkmarks & 7 red crosses. However, one of the green checkmarks is replaced by the 8th cross.

**Code**:
```python
from manimlib import *

# Files: green.png, red.png in same folder as this script

class MyScene(Scene):
def construct(self):
nodes = [ImageMobject(f"./green.png") for i in range(35)] + [ImageMobject(f"./red.png") for i in range(7)]
network = Group(*nodes).arrange_in_grid().scale(0.2)
self.add(network)
```

**Wrong display or Error traceback**:

### Additional context
When I run this code on my laptop, I still get the wrong amount of each picture, but the incorrect one is in a different spot in the grid.

Look at the ImageMobject class in manimlib/mobject/types/image_mobject.py. The bug likely involves image caching or incorrect assignment when many instances are created. Run the provided script to reproduce the issue, then examine how images are loaded and stored. Check for shared references or mutable state. A test can be added to verify the fix ensures each ImageMobject displays the correct file.

Scritto dal modello di indicizzazione a partire dal testo della issue.