Bug fix to log model checkpoints as artifacts

[manangoel99]

Description

This PR fixes the WandbLogger.log_artifact method which was initially overwriting the provided artifact argument. Moreover, in order to save models as artifacts, it adds the runner.log_artifact call to the CheckpointCallback.

Related Issue

Fixes #1427

Type of Change

• [ ] Examples / docs / tutorials / contributors update
• [x] Bug fix (non-breaking change which fixes an issue)
• [x] Improvement (non-breaking change which improves an existing feature)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

PR review

Anyone in the community is free to review the PR once the tests have passed. If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Checklist

• [ ] Have you updated tests for the new functionality?
• [ ] Have you added your new classes/functions to the docs?
• [x] Have you updated the CHANGELOG?
• [ ] Have you run colab minimal CI/CD with latest requirements? Please attach the notebook link.
• [ ] Have you run colab minimal CI/CD with minimal requirements? Please attach the notebook link.
• [ ] Have you checked XLA integration? Please attach the notebook link.
• [ ] Have you checked distributed XLA integration? Please attach the notebook link.

[CLAassistant]

All committers have signed the CLA.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.