Flowdocument's image memory usage exception

### Description

In richtextbox, pasting a lot of images, or embedding custom controls can cause memory spikes. This can be solved if you set the cache mode for images to none. But you can't set it for pasted-in images.

BitmapImage img = new BitmapImage(new Uri());
img.CacheOption = BitmapCacheOption.None;

### Reproduction Steps

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### Expected behavior

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### Actual behavior

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### Regression?

_No response_

### Known Workarounds

_No response_

### Impact

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### Configuration

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### Other information

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