CNDB-13408 Improve BM25 test with better logic (#1963)

[djatnieks]

Code to generate collection values for BM25 test is difficult to follow. This commit refactors the generation code into methods with simpler code. Also this commit removes unused last column in the dataset.

[github-actions]

Checklist before you submit for review

• This PR adheres to the Definition of Done
• Make sure there is a PR in the CNDB project updating the Converged Cassandra version
• Use NoSpamLogger for log lines that may appear frequently in the logs
• Verify test results on Butler
• Test coverage for new/modified code is > 80%
• Proper code formatting
• Proper title for each commit staring with the project-issue number, like CNDB-1234
• Each commit has a meaningful description
• Each commit is not very long and contains related changes
• Renames, moves and reformatting are in distinct commits
• All new files should contain the DataStax copyright header instead of the Apache License one

[driftx]

As I recall there are already some failing BM25 tests, maybe this will help.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cassci-bot]

❌ Build ds-cassandra-pr-gate/PR-1977 rejected by Butler

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1 regressions found
See build details here

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Found 1 new test failures

Test	Explanation	Runs	Upstream
o.a.c.distributed.test.repair.ForceRepairTest.forceWithDifference ()	REGRESSION	🔴	1 / 2

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Found 11 known test failures