* Rename `auto_pvary` to `auto_pcast` since it disables more than just pvarys.
* Skip inserting pvarys in more places if auto_pcast is False.
* Also rename standard_insert_pvary to auto_insert_reshard since this function does more stuff than just inserting pvarys.
* Also expose `jax.auto_pcast` config.
PiperOrigin-RevId: 913777481