CNDB-15312: Fix multi-column partition key CQL generation in DataRange

[driftx]

What is the issue

Multi-column partition keys generate invalid CQL

What does this PR fix and why was it fixed

Fix multi-column partition key CQL generation in DataRange.toCQLString()

When isSinglePartition() is true for composite partition keys, generate valid CQL like "k1 = 1 AND k2 = 2" instead of invalid "k1, k2 = 1, 2".

Adds test coverage for multi-column partition key scenarios.

[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

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cassci-bot]

❌ Build ds-cassandra-pr-gate/PR-1996 rejected by Butler

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10 regressions found
See build details here

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Found 10 new test failures

Test	Explanation	Runs	Upstream
replica_side_filtering_test.TestAllowFiltering.test_consistent_wide_table (offheap-bti)	REGRESSION	🔴	0 / 4
replica_side_filtering_test.TestAllowFiltering.test_count (offheap-bti)	REGRESSION	🔴	0 / 4
o.a.c.cql3.validation.operations.AggregationQueriesTest.testAggregationQueryShouldNotTimeoutWhenItExceedesReadTimeout (compression)	REGRESSION	🔴	2 / 4
o.a.c.db.AbstractReadQueryToCQLStringTest.testLiterals (compression)	REGRESSION	🔴	0 / 4
o.a.c.db.AbstractReadQueryToCQLStringTest.testSkinnyTable (compression)	REGRESSION	🔴	2 / 4
o.a.c.db.AbstractReadQueryToCQLStringTest.testSkinnyTableWithMulticolumnKey (compression)	REGRESSION	🔴	2 / 4
o.a.c.db.AbstractReadQueryToCQLStringTest.testWideTable (compression)	REGRESSION	🔴	3 / 4
o.a.c.db.AbstractReadQueryToCQLStringTest.testWideTableWithMulticolumnKey (compression)	REGRESSION	🔴	3 / 4
o.a.c.db.ReadCommandTest.testToCQLString (compression)	REGRESSION	🔴	0 / 4
o.a.c.metrics.TrieMemtableMetricsTest.testContentionMetrics (compression)	REGRESSION	🔴	0 / 4

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Found 4 known test failures

[djatnieks]

Check if the regressions reported by Butler for ReadCommandTest.testToCQLString and AbstractReadQueryToCQLStringTest might be related to these changes or are something else.

[driftx]

Those are the ones that will get fixed in #15304 which needs this.

[driftx]

Looking more closely, you were correct. I'll include the simple fix in 15304.