[2.1] Revert renaming method onMaster() and offMaster() in interface LocalNodeMasterListener

[tlfeng]

Description

Backport PR #3686 to 2.1 branch.

Revert renaming method onMaster() and offMaster() in interface LocalNodeMasterListener

I didn't realize that the onMaster() and offMaster() is exposed to the public, then renamed it directly to make the method name inclusive. The classes that implement the interface need to implement the method in new name, so it breaks backwards compatibility.
The original file: https://github.com/opensearch-project/OpenSearch/blob/2.0.1/server/src/main/java/org/opensearch/cluster/LocalNodeMasterListener.java

Issues Resolved

#3688

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[opensearch-ci-bot]

✅   Gradle Check success d0ea8e6
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Reports 6283