log spam on vulkan when window is minimized

[aclysma]

See aclysma/skulpin#92

We should address the TODO:

//TODO: This can occur persistently when the app is minimized, so ignore
// if the size has not changed. However, we could also consider adding
// a counter to limit the frequency. (A sensible case for this is
// resizing a window - to avoid rebuilding swapchain every frame during
// the resize.