Adds checks to tf.nn.sparse_softmax_cross_entropy_with_logits to make sure...

Adds checks to tf.nn.sparse_softmax_cross_entropy_with_logits to make sure that shapes for labels and logits (except last dimension) match. First, the static dimensions are checked, and only if the result is inconclusive a dynamic check is added.

In sparse_softmax_cross_entropy_with_logits the input dimensions are flattened, which can lead to unexpected bugs if the order of dimensions does not match (e.g. if one is time-major and the other is batch-major). This prevents such mistakes.

PiperOrigin-RevId: 187841750