nightly-2024-05-02: feat: Complex outputs from acir call (#4952)

# Description

## Problem\*

Resolves #4608 

## Summary\*

The change ended up being quite simple where we just have to call the
flattened size on the type rather than `try_get_array_length`. We type
check that any other types such as slices or references are not returned
from the foldable function being called so this call is safe to do. A
test was also included in `fold_complex_outputs` that checks whether we
are able to successfully modify a complex struct in a foldable function
correctly.

## Additional Context



## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [x] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.