Convert tf.FusedBatchNorm into tfl primary math ops

* Added TF::FusedBatchNormOp
* Validated TF::FusedBatchNormOp's operands
* Added converter from tf.FusedBatchNorm to tfl math ops

In the converter, we additionally check that the 'is_training'
attribute in tf.FusedBatchNorm is false and the last 4 outputs
are all not used (true for inference). These requirements do
not exist in the original TOCO source code, which just silently
ignores the last 4 outputs.

PiperOrigin-RevId: 223027333