Replace runtime.EnumRange with runtime.Set

[5nord]

The possible values of an enumeration do not need to be represented by their own runtime-object type. They actually are just "value constraints", which can be modeled as a set-template (runtime.NewSet).

Originally posted by @5nord in https://github.com/nokia/ntt/pull/637#discussion_r985197239

[github-actions[bot]]

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