feat: Add array_refcount and slice_refcount builtins for debugging

[jfecher]

Description

Problem*

Resolves

Summary*

Added debug functions to retrieve the hidden reference count field on arrays and slices in unconstrained code. This always returns 0 in constrained and comptime code.

Additional Context

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

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