Updating `Image::data` does not change how the image is displayed in `StandardMaterial`.

## Bevy version

0.15

## What you did

Update an existing `Image`'s `data` after it has been created and rendered at least once.

## What went wrong

`StandardMaterial` did not update its render, despite the content of the `Image` asset has changed.

## Additional information

Reproduction:
https://github.com/mintlu8/bevy_bug

Start with the linked reproduction and trace how an existing Image's data update reaches StandardMaterial rendering. Inspect the asset-update and image-rendering paths involved in the reproduction. Done means changing Image data after its first render reliably changes the displayed material image, with a regression test if the relevant test location can be identified.

Written by the indexing model from the issue text.