* Add traits for witness and committed instance
* Implement witness and committed instance traits for Nova and HyperNova
* Implement witness and committed instance traits for ProtoGalaxy
* Improve the clarity of docs for `Witness{Var}Ext::get_openings`
* Avoid cloning `z_i`
* Fix grammar issues
* Rename `Ext` traits for committed instances and witnesses to `Ops`
* Implement `to_sponge_bytes`