feat: correct origins for `CombinedCallGraphNodes`

[lukarade]

Closes #267

Summary of Changes

[github-actions[bot]]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	black	12	0	0	1.81s
✅ PYTHON	mypy	12		0	3.76s
✅ PYTHON	ruff	12	0	0	0.06s
✅ REPOSITORY	git_diff	yes		no	0.06s

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 89.00000% with 11 lines in your changes missing coverage. Please review.

Project coverage is 92.87%. Comparing base (492134e) to head (1737a01). Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
...er/processing/api/purity_analysis/model/_purity.py	84.78%	7 Missing :warning:
...cessing/api/purity_analysis/_resolve_references.py	85.00%	3 Missing :warning:
...er/processing/api/purity_analysis/_infer_purity.py	93.33%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #269 +/- ## ========================================== - Coverage 92.94% 92.87% -0.07% ========================================== Files 98 98 Lines 6818 6853 +35 ========================================== + Hits 6337 6365 +28 - Misses 481 488 +7 ```

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[lars-reimann]

@lukarade I'll review after the conflicts are resolved.

[lukarade]

@lukarade I'll review after the conflicts are resolved.

@lars-reimann Done.

[lukarade]

Very nice, just a few requests regarding types in the documentation.

Since we talked about that on multiple occasions before, and for consistency, all type hints from docstrings were removed.