Should DataTree.orphan act in-place?

[TomNicholas]

What is your issue?

DataTree.orphan remove the parent node from a tree, but modifies in-place. It has no return value, so it's already consistent with #9196. But it's not obvious to me whether or not the method should return a modified copy instead.

came up here #9666 (comment)

cc @keewis @shoyer

[shoyer]

I have had similar thoughts.

The non-inplace version is currently spelled DataTree.copy(). But the name is not so intuitive.

Something like tree['child'].orphan(inherit=False) would be much cleaner than tree['child'].copy(inherit=False).