[jax2tf] Fix out-of-bounds errors for dynamic slices (#3649)
* [jax2tf] Fix out-of-bounds errors for dynamic slices
JAX and XLA clamp dynamic out-of-bounds indices. Reproduce that
behavior by forcing the use of XLA for tf.dynamic_slice.
We choose this solution for now for consistency with how we handle
gather. We may decide to switch to explicitly clamping indices.
Fixes: #3621
