Auto virtual texture import can be confusing for some users

There have been a few times internally and with licensees where people have enabled virtual texturing on a project to access RVT and then have been surprised when textures start to be imported as streaming virtual textures.

This happens because:
Auto Virtual Texturing Size defaults to something quite small (4096)
Auto Virtual Texturing Size is in the Editor Texture Import part of project settings, not with the other VT settings in Engine Rendering.

I propose that we add a Auto Import checkbox under Engine Rendering defaulted to off.

This changes default behavior. If that's not allowed in this case we would need to default the new setting to on. But at least it would be more visible.

Enable or disable the new "Enable virtual texture on import" project setting.

Try importing a large (8K or bigger) texture asset.

Check that the new texture asset is marked as VT or not according to the new setting.