Adding a priority option to kernels in order to be able to override Device...

Adding a priority option to kernels in order to be able to override Device selection prioritization. For the regular case, we always prefer to place on the GPU but for tf.data pipelines when no device is specified, we'd like to place it on the CPU actually since that is what the user usually intends.

As we extend parts of the tf.data pipeline to run on GPU's / TPU's etc., this will become more and more necessary.

PiperOrigin-RevId: 221264064