Preserve plugin-managed indices during integration test cleanup

[ahkcs]

Description

Prevents per-class integration test cleanup from deleting plugin-managed indices.

In release integration test run 11379, the secured SQL suite took 4h44m versus 41m without security. The secured cluster log shows cleanup deleting and forcing recreation of security-auditlog-* 358 times, once per test-class cleanup, along with 575 audit-indexing errors. Many of those errors were generated by attempted deletion of protected ML and geospatial indices.

This change extends the existing system-index filter to preserve the observed plugin-managed prefixes. Ordinary test indices, including unrelated hidden test indices, remain eligible for cleanup.

A representative secured A/B run of SQLCursorPermissionsIT showed:

• Unmodified main: audit index created, deleted by cleanup, then recreated.
• This branch: audit index created once and preserved; no audit-index deletion or recreation.

The next distribution integration run will provide the full-suite runtime measurement.

Related Issues

Follow-up to #5620

Testing

• ./gradlew :integ-test:spotlessJavaCheck :integ-test:compileTestJava --no-daemon
• ./gradlew :integ-test:integTest --tests "org.opensearch.sql.legacy.OpenSearchSQLRestTestCaseIT" -DignorePrometheus=true --no-daemon
• ./gradlew :integ-test:integTestWithSecurity --tests "org.opensearch.sql.security.SQLCursorPermissionsIT" --no-daemon

Check List

• New functionality includes testing.
• New functionality has been documented.
• New functionality has javadoc added.
• New functionality has a user manual doc added.
• New PPL command checklist all confirmed.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff or -s.
• Public documentation issue/PR created.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 PR contains tests

🔒 No security concerns identified

📝 TODO sections integ-test/src/test/java/org/opensearch/sql/legacy/OpenSearchSQLRestTestCase.java [229]: Ignore index delete error for now. Remove if strict check on system index

🔀 No multiple PR themes

⚡ No major issues detected

[github-actions]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
General	Add null check for parameter Add null check for indexName parameter to prevent NullPointerException when the method is called with null. This is a defensive programming practice that prevents potential runtime errors during index cleanup operations. integ-test/src/test/java/org/opensearch/sql/legacy/OpenSearchSQLRestTestCase.java [239-241] static boolean isPluginManagedIndex(String indexName) { + if (indexName == null) { + return false; + } return PLUGIN_MANAGED_INDEX_PREFIXES.stream().anyMatch(indexName::startsWith); } Suggestion importance[1-10]: 3 __ Why: While adding a null check is a defensive programming practice, the indexName is extracted from a JSON response in the calling code (line 223), making null unlikely. The suggestion addresses a minor edge case but doesn't fix a critical issue.	Low