Allow for loops over non-comptime ranges in unconstrained functions

[jfecher]

Problem

The purpose of unconstrained functions is to allow non-deterministic features, most notably arrays of unknown (at compile-time) length and loops over unknown bounds. Yet, this is currently disallowed by the type checker.

Proposed solution

Relax the comptime Field check in the typechecker for for loop ranges to just Field if we are currently inside an unconstrained function.

Alternatives considered

No response

Additional context

No response

Submission Checklist

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