Moves for loop handling to a function. (#5587)

## Description

An issue was reported by @sdankel on #5477 caused by #5557.

A segmentation fault would occur when the for loop handling was
performed inside the match. This would occur even when that part of the
code was not called. Looks like a weird rust issue.

## Checklist

- [ ] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [ ] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

Co-authored-by: Igor Rončević <[email protected]>