Consider revising the _repr_inline_ protocol

[shoyer]

_repr_inline_ looks like an IPython special method but is actually includes some xarray specific details: the result should not include shape or dtype.

As I wrote in #5352, I would suggest revising it in one of two ways:

1. Giving it a name like _xarray_repr_inline_ to make it clearer that it's Xarray specific
2. Include some more generic way of indicating that shape/dtype is redundant, e.g,. call it like obj._repr_ndarray_inline_(dtype=False, shape=False)