feat(brillig_gen): Return slices from foreign calls

[vezenovm]

Description

Problem*

Partial works towards #1556

Summary*

Now that slices are implemented on the frontend and in the SSA refactor we need to enable code gen for both Brillig and ACIR. This some partial work towards the Brillig gen for slices that enables us to return a slice from an external call like below:

#[oracle(get_number_sequence)]
unconstrained fn get_number_sequence(_size: Field) -> [Field] {}

I have also included a test that makes two different foreign calls to verify that memory has not been overwritten and we can iterate over the dynamic slices returned from the foreign call inside Brillig.

Other work is being done in parallel to enable these dynamic slices to be returned from Brillig into ACIR and handled inside of ACIR.

Documentation

• This PR requires documentation updates when merged.

  • I will submit a noir-lang/docs PR.
  • I will request for and support Dev Rel's help in documenting this PR.

Additional Context

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[jfecher]

Looks good. Can you create an issue for the two remaining comments? Then we can merge this

[vezenovm]

Looks good. Can you create an issue for the two remaining comments? Then we can merge this

Made issues #1910 and #1911. I am working on a logging refactor right now which will resolve #1910 fully and #1911 partially.