bevy_render::Image data calculations do not account for mip levels

## Bevy version

37915e1d9370a7ea46afb3eec6d62b4074a9f120

## Info

Any `Image` size/data length related calculations such as in `new()`, `new_fill()`, `resize()`, etc do not account for mip levels.

See the wgpu docs: https://docs.rs/wgpu/latest/wgpu/util/trait.DeviceExt.html#tymethod.create_texture_with_data