Improved warning UX for bad asset cases + generated icon

[CianNoonan]

This PR is taking some design liberty on the UX.

Importantly I also now allow a smart texture to be created from images that do not match in size. This does create some artefacts as shown below but the case is warned to the end-user so they can investigate and decide what to do. In future, these inputs could maybe be resized on the CPU with a nicer algo to mitigate this issue.

Original Output

• I have implemented warnings for the following cases, clicking these warnings navigates to the asset -- Size mismatch -- Compressed input texture (The way I detect whether a format is compressed could be improved but there isn't a simple built-in check to find this out)
• Generated icon -- In order to match basic texture UX the smart textures icon is now a small version of the output texture.