[JAX] Make fully replicated sharding to avoid materializing the same host buffers
This change recognizes fully replicated shardings (based on JAX sharding), and
materialize only one host buffer. This saves the cost of repeatedly
materializing the same host buffer for multiple devices, and makes it
streamlined to create a multi-device IFRT array.
Clean up `JAX_IFRT_VERSION_NUMBER < 2` since we are well past it.
PiperOrigin-RevId: 758320113