Feature/pna 2849 handle memory explosion bug

[johandahlberg]

Description

Updating polars seems to have caused the memory usage in the graph step to explode. This PR resolves this by swapping parts of the implementation from polars to duckdb.

Fixes: pna-2894

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Manually running the graph step and verifying that the memory usage seems to be back at roughly the 0.27.0 release levels.

PR checklist:

• This comment contains a description of changes (with reason).
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• If a new tool or package is included, I have updated dependencies in pyproject.toml and cited it properly
• I have checked my code and documentation and corrected any misspellings
• I have documented any significant changes to the code in CHANGELOG.md

[ptajvar]

This looks great! Verified that the graph output remains the same.

[johandahlberg]

I also prepped there release notes here now, since we want to do a release on this straight away now.