Proto/Michelson: no comparable type in sets and maps

Context

Here are a few commits I wrote some time ago when trying to merge ty and comparable_ty. I needed to break the dependency of sets/maps modules on comparable types.

The recent round-trip issue showed it is indeed a good idea to not have values containing types. It is here done for sets and maps. Doing it for big maps is left as an exercise for the first reviewer ;-)

• I need to check whether cache sizes need to updated
  • I'd say there's nothing to do because I'm removing a value from Boxed_Set/Map and adding one to Boxed_Set/Map_OPS

Manually testing the MR

CI

Checklist

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