Mutating `rearrange!` variant

[AntonOresten]

Should just be a matter of using permutedims!.

[AntonOresten]

I guess this isn't really well defined, and requires a buffer with the output size, since reshapes cannot be mutating.

[AntonOresten]

actually I guess we don't need it to be the same instance. it's fine to create new instances with reshape since it's so cheap. the point would be the ability to permute a buffer instead of copying to a new array

[AntonOresten]

Maybe it should be rearrange!! since they would not necessarily be the same object (only when just permuting), but they still point to the same data.

[AntonOresten]

lol maybe not

[AntonOresten]

You could still do it with two arrays