test: Utility to compare two lists of documents for equality

[julian-risch]

Related Issues

contains_same_docs always returned True if the two input lists of documents had the same length. This happened because the implementation uses the return value of sort instead of sorted.
Four tests using the utility were actually broken due to issues in the implementation of the tests.

Proposed Changes:

• Use sorted instead of sort, which returns the sorted list so that it can be compared to the other sorted list of documents.
• Fix four broken tests that used the utility. Three of them contained just small mistakes. One had a problem comparing int -2 and float -2.0 for equality.

How did you test it?

Manual tests for the contains_same_docs. It's a small utility function of DocumentStoreBaseTests and I didn't want to add tests for it.
Updated unit tests.

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue