Revert "[Feature] Add PPL rest command"

[noCharger]

Description

This reverts the changes introduced by PR #5599 (merge commit 454ac4e).

Related Issues

N/A

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.

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PR Code Analyzer ❗

AI-powered 'Code-Diff-Analyzer' found issues on commit 3e6a82a.

Path	Line	Severity	Description
opensearch/src/main/java/org/opensearch/sql/opensearch/setting/OpenSearchSettings.java	643	medium	Null guard removed from registerNonDynamicSettings: the prior code only stored a value when clusterSettings.get(setting) was non-null; the new code unconditionally stores the result, which may be null. If downstream callers assume non-null values in latestSettings this can silently corrupt state or cause NullPointerExceptions under certain cluster configurations. The change is subtle and its effect is non-obvious from context, warranting review.
integ-test/src/test/java/org/opensearch/sql/sql/VectorSearchIT.java	31	low	super.init() call removed from VectorSearchIT.init(). If the parent class sets up security context, authentication state, or other shared test infrastructure, omitting this call silently skips that setup. The change is unrelated to the stated PR purpose (removing the rest command) and may cause tests to pass against a weaker or improperly initialized security posture.

The table above displays the top 10 most important findings.

Total: 2 | Critical: 0 | High: 0 | Medium: 1 | Low: 1

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[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 No relevant tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ No major issues detected

[github-actions]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
Possible issue	Add null check for settings The null check if (clusterSettings.get(setting) != null) was removed. This could cause NullPointerException if clusterSettings.get(setting) returns null. Add a null check before putting the value into the map. opensearch/src/main/java/org/opensearch/sql/opensearch/setting/OpenSearchSettings.java [643] -latestSettings.put(key, clusterSettings.get(setting)); +if (clusterSettings.get(setting) != null) { + latestSettings.put(key, clusterSettings.get(setting)); +} Suggestion importance[1-10]: 8 __ Why: Removing the null check before putting a value into latestSettings could cause a NullPointerException if clusterSettings.get(setting) returns null. This is a potential runtime error that should be addressed.	Medium
	Restore missing super.init() call The super.init() call was removed from the init() method. This may cause initialization issues if the parent class requires initialization. Verify that removing this call doesn't break the test setup or parent class contract. opensearch/src/main/java/org/opensearch/sql/opensearch/storage/system/OpenSearchSystemIndex.java [30-32] @Override protected void init() throws Exception { + super.init(); loadIndex(Index.ACCOUNT); } Suggestion importance[1-10]: 7 __ Why: The removal of super.init() could break the test setup if the parent class requires initialization. However, this appears to be intentional as part of the refactoring, and the test may still function correctly if the parent's initialization is not needed.	Medium