test(processing): migrate segment tests to JUnit 5

[FrankChen021]

Fixes #13948.

Description

Migrate Batch 3 processing tests to the current JUnit 5 APIs while preserving test behavior and compatibility. This covers segment core, serialization, incremental indexes, and the index-merger hierarchy.

The migration uses TemporaryFolderExtension, CloserExtension, and LoggerCaptureExtension, retains the existing CloserRule compatibility test, and preserves the shared DruidExceptionMatcher and ExceptionMatcher APIs.

Scope

• processing/src/test/java/org/apache/druid/segment core and index-merger tests
• segment/column, segment/data, segment/generator, segment/incremental, segment/serde, segment/shim, segment/transform, segment/vector, and segment/writeout
• No query files, shared helper changes, Batch 2 paths, CloserRule.java, or processing/pom.xml changes

Validation

• mvn -ntp -pl processing -am test-compile -Dweb.console.skip=true -T1C — passed with Checkstyle, PMD, forbidden APIs, enforcer, and compilation checks
• mvn -ntp -pl processing spotbugs:check -Dweb.console.skip=true — passed with 0 bugs and 0 errors (SpotBugs reported one missing optional MarkerManager class during analysis)
• Focused Batch 3 migration tests — 112 tests passed, 0 failures, 1 intentionally disabled
• git diff --check and scope audits — passed

The broader parameterized Schemaless run was not stable on the local OpenJDK 25 environment: it reproduced intermittent direct-buffer Unsafe SIGSEGVs and two parameterized-instance flakes that also occurred when the class was run in isolation. No source assertion failure was isolated.

Key changed/added classes in this PR

• Segment core and index-merger tests
• Column, data, incremental-index, serde, transform, vector, and writeout tests
• CloserRuleTest compatibility coverage

This PR has:

• been self-reviewed.
• added or updated unit tests (existing tests migrated while preserving coverage).

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[FrankChen021]

Addressed the CodeQL array-bound finding in the current Batch 3 branch (head 98eab35): split the null and non-null loops so each array access is statically bounded by the corresponding array length. The focused FixedIndexedTest cases pass. The current token cannot execute GitHub inline review replies or resolveReviewThread, so this top-level response records the fix.

[FrankChen021]

The targeted retry (workflow attempt 2) reproduced the same unrelated environment failure: SchemalessTestSimpleTest intermittently failed testFullOnTimeseries/testFullOnSearch, then the Zulu OpenJDK 25.0.4 VM terminated with SIGSEGV (exit 134). The migration change is not on this stack; I will make one further targeted retry after GitHub finalizes the run.

[FrankChen021]

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

Reviewed 56 of 56 changed files.

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This is an automated review by Codex GPT-5.6-Luna(max)

[FrankChen021]

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

Reviewed 55 of 55 changed files.

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This is an automated review by Codex GPT-5.6-Luna(max)