Recursion unrolling for functions

[lukaszcz]

• Depends on PR Check for recursive inductive types in the GEB pipeline #1909
• Closes Support recursive functions in the GEB backend #1750
• Adds recursion unrolling tests on JuvixCore
• Adds a version of the mid-square hash example without the recursion manually unrolled

For now, the recursion is always unrolled to a fixed depth (140). In the future, we want to add a global option to override this depth, as well as a mechanism to specify it on a per-function basis. In a more distant future, we might want to try deriving the unrolling depth heuristically for each function.

[janmasrovira]

nice!