[XLA:Python] Add python function to convert `xla::LiteralProto` into a tuple-tree of `numpy.ndarray`.
[XLA:Python] Add python function to convert `xla::LiteralProto` into a tuple-tree of `numpy.ndarray`.

This is intended for internal debugging use. It cannot be used on OSS because the relevant protobufs are not part of the public API. (Though it must not break the OSS build, naturally.)
