Vectorize SpectatorHistogram

[jtuglu1]

Description

Vectorizes SpectatorHistogram.

Performance

Need to do real-world testing (TODO), but benchmarks are promising (>10x speed-up):

Benchmark                                                    (metricName)  (rowsPerSegment)  (vectorize)  Mode  Cnt      Score   Error  Units
SpectatorHistogramAggregatorBenchmark.queryIncrementalIndex         long1           1000000        false  avgt    2  92451.646          us/op
SpectatorHistogramAggregatorBenchmark.queryIncrementalIndex         long1           1000000         true  avgt    2  73224.875          us/op
SpectatorHistogramAggregatorBenchmark.queryQueryableIndex           long1           1000000        false  avgt    2   3776.303          us/op
SpectatorHistogramAggregatorBenchmark.queryQueryableIndex           long1           1000000         true  avgt    2    202.916          us/op

Other perf ideas

• Possibly apply some fixed step loop unrolling to save even more instructions.

Release note

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Key changed/added classes in this PR

• MyFoo
• OurBar
• TheirBaz

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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.

[jtuglu1]

Test failure is unrelated and being fixed in #18814