[BUG] Classes that extend class 'o.o.action.support.master.TransportMasterNodeAction' should not have to implement abstract method 'clusterManagerOperation()'

[tlfeng]

Describe the bug
Similar issue: #3663 and #3688
Introduced by PR #3617 / commit 60d7a09, which aims to resolve issue #3542

The problem:
To deprecate public methods that has "master" in the name, I created an alternative method clusterManagerOperation(...) to replace masterOperation(...), which is an abstract method.
Location: https://github.com/opensearch-project/OpenSearch/blob/157e69330891b8133d56ab993b5022f2e8c6ee04/server/src/main/java/org/opensearch/action/support/clustermanager/TransportClusterManagerNodeAction.java
It makes classes that extend the class TransportMasterNodeAction have to implement the newly added abstract method clusterManagerOperation(...), and it breaks the backwards compatibility.

The solution is to revert the changes to remove the abstract method clusterManagerOperation(...).

To Reproduce
Build k-NN plugin with OpenSearch 2.1.0 (the code at https://github.com/opensearch-project/OpenSearch/tree/304d830275fdbe5f8095a7285ca66266987c727a)

java.lang.AbstractMethodError: Missing implementation of resolved method 'abstract void clusterManagerOperation(org.opensearch.action.support.clustermanager.ClusterManagerNodeRequest, org.opensearch.cluster.ClusterState, org.opensearch.action.ActionListener)' of abstract class org.opensearch.action.support.clustermanager.TransportClusterManagerNodeAction. » at org.opensearch.action.support.clustermanager.TransportClusterManagerNodeAction.clusterManagerOperation(TransportClusterManagerNodeAction.java:135) » at org.opensearch.action.support.clustermanager.TransportClusterManagerNodeAction$AsyncSingleAction.lambda$doStart$3(TransportClusterManagerNodeAction.java:223)

Expected behavior
k-NN plugin should successfully be built with OpenSearch 2.1.0

Additional context
Add any other context about the problem here.

[tlfeng]

The solution has been applied to 2.1 branch by the PR #3682, the problematic change has been reverted.

[tlfeng]

Close the issue. The masterOperation() method name have been restored in all branches.
PR #3681 for main branch, and PR #3714 for 2.x branch.

[tlfeng]

I have got a solution from @andrross to properly deprecate the abstract method 'masterOperation()'.

@Deprecated("override doSomethingWithClusterManager instead")
void doSomethingWithMaster() {
    throw new UnsupportedOperationException("Must be overridden");
}

void doSomethingWithClusterManager() {
    doSomethingWithMaster();
}

The below is wrong because it will break any child classes.

@Deprecated("override doSomethingWithClusterManager instead")
abstract void doSomethingWithMaster();

abstract void doSomethingWithClusterManager();

[tlfeng]

The final solution in PR #4032 has been merged, and from version 2.2.0, developers can use clusterManagerOperation() to replace masterOperation().
For more detail: #3542 (comment)