fix: Repair invalid schema arising from lowering pass

[gs-olive]

Description

• When remove_unnecessary_casts replaces both tensors in an aten::div call with the corresponding scalars, and the rounding mode (third argument) is specified, the schema becomes invalid
• To avoid this, we intercept the call and split the result based on what the third argument in the input was, either delegating the result to aten::Int(aten::div(...)), for "trunc" or aten::floordiv(...) for "floor"
• Update lowering pass to incorporate the above change, with appropriate documentation
• Add testing to verify catching and correctly handling these edge cases

Fixes #1780

Type of change

Please delete options that are not relevant and/or add your own.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• [ x ] My code follows the style guidelines of this project (You can use the linters)
• [ x ] I have performed a self-review of my own code
• [ x ] I have commented my code, particularly in hard-to-understand areas and hacks
• [ x ] I have made corresponding changes to the documentation
• [ x ] I have added tests to verify my fix or my feature
• [ x ] New and existing unit tests pass locally with my changes
• [ x ] I have added the relevant labels to my PR in so that relevant reviewers are notified

[narendasan]

LGTM