`arange` should return empty array if bounds are inconsistent with step sign

[pmeier]

The array API specification stipulates that the following should hold for the return value of torch.arange:

The length of the output array must be ceil((stop-start)/step) if stop - start and step have the same sign, and length 0 otherwise. We currently bail out:

>>> torch.arange(1, 0)
RuntimeError: upper bound and larger bound inconsistent with step sign

cc @gchanan @mruberry @rgommers @pmeier @asmeurer @leofang @AnirudhDagar @asi1024 @emcastillo @kmaehashi

[rgommers]

Thanks @pmeier. I think this is fairly low prio to fix, but a sensible and useful design change in its own right (for the same reason empty tensor / empty batchdim etc. are useful) so we should change it.