[FEATURE] Remove $ref expansion from structured_output

[zastrowm]

Problem Statement

We currently have two ways of generating function specs for objects:

1. An implementation for Decorators
2. An implementation for structured_output

We've updated (1) to include $refs as-as, but (2) expands $refs, which leads to bugs like #337 as we're not very complete about it.

Proposed Solution

Move away from expanding refs in structured_output

Use Case

N/A

Alternatives Solutions

No response

Additional Context

No response