[aot] Fixed vulkan texture usage export (#6519)
[aot] Fixed vulkan texture usage export (#6519)

`alloc_info.usage` is the usage of memory allocation, to inform VMA how
we gonna use the memory (for example, is it host accessible?) While
`image_info.usage` is the one that should be exported.
yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi