Proto: minor cleanups
Minor simplifications, mostly cherry-picked from branch https://gitlab.com/nomadic-labs/tezos/-/tree/guillaume-claret-coq-of-ocaml-simplifications by @clarus1
Minor simplifications, mostly cherry-picked from branch https://gitlab.com/nomadic-labs/tezos/-/tree/guillaume-claret-coq-of-ocaml-simplifications by @clarus1