feat: multi-scale SSIM

[R055A]

Description

Add feature: multi-scale SSIM

Related Issue

Fixes #359

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Unit testing

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Additional Notes

---

Note

Adds msssim metric via TorchMetricWrapper, generalizes ssim_update to support SSIM and MS-SSIM, and adds targeted tests (type mapping, invalid params).

• Metrics:
  • Add MultiScaleStructuralSimilarityIndexMeasure import and new enum entry TorchMetrics.msssim using pairwise_y_gt and shared ssim_update.
  • Generalize ssim_update to accept StructuralSimilarityIndexMeasure | MultiScaleStructuralSimilarityIndexMeasure and handle float casting.
• Tests:
  • Add tests ensuring TorchMetricWrapper('ssim') and ('msssim') instantiate the correct metric types.
  • Add negative tests validating invalid parameter combinations for SSIM/MS-SSIM raise ValueError.

^{Written by Cursor Bugbot for commit 5e8558f. This will update automatically on new commits. Configure here.}

[begumcig]

Thanks a lot @R055A, looks almost perfect to me! How about we add some tests in pruna/tests/evaluation/test_torch_metrics.py for this metric?

[R055A]

Thanks a lot @R055A, looks almost perfect to me! How about we add some tests in pruna/tests/evaluation/test_torch_metrics.py for this metric?

Added 6 test cases @begumcig

[begumcig]

Thank you so much for the updates, looks great!

[R055A]

Thank you so much for the updates, looks great!

Thank you. I just now fixed the lint error

[johannaSommer]

Test failures are due to the HF servers and not related to this PR, ready to merge ☑️