Add cluster command for PPL

[ritvibhatt]

Description

[Describe what this change achieves]

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

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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[github-actions]

PR Code Analyzer ❗

AI-powered 'Code-Diff-Analyzer' found issues on commit 8f2804e.

Path	Line	Severity	Description
core/src/main/java/org/opensearch/sql/calcite/udf/udaf/ClusterLabelAggFunction.java	172	low	System.err.println used for error output instead of a logging framework. While not malicious, this could leak internal cluster IDs and exception messages to stderr in production environments and represents an anomaly compared to the rest of the codebase.

The table above displays the top 10 most important findings.

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

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[github-actions]

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