Updating texture size is not properly reflected on materials.

## Bevy version and features

0.19.1

## What you did

Updating a texture without triggering change detection on a material. This used to not work but in 0.19 it works partially if the texture size stayed the same.

## What went wrong

This works as expected if the texture size did not change, but behaves as if the texture size stayed the same but contents changed if the texture size gets updated.

Start by reproducing the texture update described for Bevy 0.19.1, comparing updates that preserve the texture size with updates that change it. Trace how texture size changes reach materials and add coverage showing that materials reflect the new dimensions; done means both cases behave consistently.

Written by the indexing model from the issue text.