Buffer from_iter method is inconsistent across buffer implementations

[maplant]

CpuAccessibleBuffer defines its from_iter method with the following signature:

pub fn from_iter<I>(
    device: Arc<Device>, 
    usage: BufferUsage, 
    data: I
) -> Result<Arc<CpuAccessibleBuffer<[T]>>, DeviceMemoryAllocError> 

However, ImmutableBuffer defines it with a slightly different ordering:

pub fn from_iter<D>(
    data: D, 
    usage: BufferUsage, 
    queue: Arc<Queue>
) -> Result<(Arc<ImmutableBuffer<[T]>>, CommandBufferExecFuture<NowFuture, AutoCommandBuffer>), DeviceMemoryAllocError> 

The issue here is that data is the last parameter in CpuAccessibleBuffer's method, while in ImmutableBuffer's method it is the first. This ordering is inconsistent and would benefit from a change.

[Rua]

This is solved by #2127.