for dynamically-sized TensorArray inside `tf.function`.
*   `tf.math`:
    *   Narrow down `argmin`/`argmax` contract to always return the smallest
        index for ties.
    *   `tf.math.reduce_variance` and `tf.math.reduce_std` return correct
        computation for complex types and no longer support integer types.
    *   Add Bessel functions of order 0,1 to `tf.math.special`.