Preserve CHLO ops through serialization

[GleasonK]

Request description

This is indirectly a feature request to preserve chlo ops from jax.export since there are some ops that simplify pattern matching (i.e. chlo.erf / erfc).

One possible way to implement this would be to wrap CHLO ops as a composite, and convert known composites back to CHLO upon deserialization. We could tag certain CHLO ops with an MLIR trait like SerializeAsComposite, and all ops that have this trait will be converted to/from a composite.

cc @vamsimanchala