feat: implement `clip_grad_norm`

[NripeshN]

Proposed changes

Closes #1040 Closes https://github.com/ml-explore/mlx/issues/1045

Checklist

Put an x in the boxes that apply.

• [x] I have read the CONTRIBUTING document
• [x] I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have updated the necessary documentation (if needed)

[NripeshN]

@awni Tests pass locally, ready to merge