Fix PRO metric calculation on GPU

[blaz-r]

Description

Fixes PRO metric calculation on GPU by changing type to float, as well as matches shapes so it works with predictions of shape N, H, W.
I also adjusted tests to verify that it does works with relevant shapes and types.

• Fixes [Bug]: PRO metric calculation fails on GPU #1316

Changes

Describe the changes you made

• Bug fix (non-breaking change which fixes an issue)
• Refactor (non-breaking change which refactors the code base)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Checklist

Ensure that you followed the following

• I have added a summary of my changes to the CHANGELOG (not for minor changes, docs and tests).
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas (If applicable)
• I have made corresponding changes to the documentation (If applicable)
• I have added tests that prove my fix is effective or that my feature works (If applicable)

[samet-akcay]

Thanks for addressing this @blaz-r. I only have a single, very minor comment.

[samet-akcay]

lgtm, thanks!