CNDB-16051: Include pq vectors in CompactionGraph bytesUsed calculation

[michaeljmarshall]

What is the issue

Fixes: https://github.com/riptano/cndb/issues/16051

What does this PR fix and why was it fixed

The SAI segment builder logic keeps track of bytes used by a segment builder to ensure proper flushing to prevent OOM. This change tracks the PQ and BQ vector byte utilization per insertion.

At the moment, the added test ensures coverage, but fails due to recall issues. I will investigate this before merging.

[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-2144 rejected by Butler

---

3 regressions found
See build details here

---

Found 3 new test failures

Test	Explanation	Runs	Upstream
o.a.c.db.compaction.unified.ShardedMultiWriterTest.testShardedCompactionWriter_threeShard[isReplicaAware=true] (compression)	REGRESSION	🔴	0 / 19
o.a.c.index.sai.cql.VectorCompaction100dTest.testOneToManyCompactionTooManyHoles[eb false]	NEW	🔴	0 / 19
o.a.c.index.sai.cql.VectorSiftSmallTest.testSiftSmall[dc false]	REGRESSION	🔴	0 / 19

---

Found 2 known test failures