fix(aten::cat): support neg dim for cat

[narendasan]

Description

Adds support for negative dim for cat

Fixes #541

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:

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

[github-actions]

Code conforms to C++ style guidelines

[github-actions]

Code conforms to Python style guidelines