Review treatment of `__array__` attribute

[ctrueden]

I'm writing this issue from memory after finding an old note to myself that I wrote in response to a conversation I had with @tlambert03 some time last year. 😅

• The imagej.images.is_arraylike function checks for four attributes: shape, dtype, __array__, and ndim. Is this correct?

• The classes that augment Java-side net.imglib2.RandomAccessibleInterval and related objects to be more arraylike include implementations of shape, dtype, and ndim on the appropriate superinterfaces, but nothing implements __array__. Should it?

Ideas and opinions welcome!