chore: Add remaining slice methods to the interpreter

[jfecher]

Description

Problem*

Summary*

Adds the remaining builtin slice methods to the interpreter.

Also adds is_unconstrained which always returns true. This way comptime can also take advantage of any if is_unconstrained() optimizations (like break) used in unconstrained code in called functions.

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.