Stop training when tf.data.Dataset objects run out of data and steps_per_epoch...

Stop training when tf.data.Dataset objects run out of data and steps_per_epoch is specified. If steps_per_epoch is not specified, the number of steps needed to reach the end of the dataset is used as the target steps for epochs after the first one. Also added a warning explaining the situation.

PiperOrigin-RevId: 234720553