minor: Add segment debug logging to CachingClusteredClient

[cecemei]

Description

When debugging slow or incorrect queries on the broker, it's useful to know how many segments were found during timeline lookup and how they break down by interval, version, and server type (realtime vs historical).

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This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[FrankChen021]

I have reviewed the code for correctness, edge cases, concurrency, and integration risks; no issues found.

Reviewed 1 of 1 changed files.

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This is an automated review by Codex GPT-5.5

[FrankChen021]

Severity	Findings
P0	0
P1	0
P2	1
P3	0
Total	1

Reviewed 1 of 1 changed files.

Found 1 issue: debug logging can emit synthetic segment IDs for sliced timeline lookups.

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This is an automated review by Codex GPT-5.5

[FrankChen021]

[P2] Log real segment IDs, not query slices

The debug log rebuilds a SegmentId from SegmentDescriptor.getInterval(), but computeSegmentsToQuery fills that descriptor from TimelineObjectHolder.getInterval(). VersionedIntervalTimeline.lookup trims the first or last holder to the requested interval, so a query over one day inside a week-long segment logs a synthetic segment id that never existed. Use s.getServer().getSegment().getId() for the segment id, and log the query interval separately if needed.