We are unshadowing non-nested lambdas only because of Apalache

[bugarela]

Our first approach to unshadowing is quite drastic: add a scope suffix (_123 in varname_123) to all lambda parameters and let definitions. This is not ideal, as these suffix will appear on some places: like the generated TLA+ version or, now, the new nondetPicks fields.

In the unshadower improvement I'm working on, we stop unshadowing things that are not nested, which is unnecessary. However, I found that this breaks the translation to ApalacheIR in some specific cases like this:

set.filter(e => f(e)).forall(e => g(e))

because the operators: forall, exists, filter, map and mapBy are translated as bindings, so the result looks like:

∀e ∈ ({e ∈ set): f(e)}): g(e): e.

And there is shadowing of e there, although there is no shadowing in the Quint version