Use the mesh of `out_aval` when converting GSPMDSharding to NamedSharding. This makes sure that the axis types of the corresponding output is correct.
Also, if all axes of an out_aval are auto, set the corresponding out_sharding to Unspecified during lowering, otherwise things go horribly wrong. This is actually a XLA bug but we can workaround it in JAX for now.
PiperOrigin-RevId: 729307115