[improve][admin] Clusters list API return clusters with local flag

[Technoboy-]

Fixes #20581
PIP: #20614

Motivation

After configuring the geo-replication on Pulsar clusters, the clusters list API will return multiple clusters, including the local Pulsar cluster and remote clusters like

bin/pulsar-admin clusters list
us-west
us-east
us-cent

But in this return, you can't distinguish the local and the remote cluster. When you need to remove the geo-replication configuration, it will be hard to decide which cluster should be removed on replicated tenants and namespaces unless you record the cluster information.

Modification

Add local flag to distinguish clusters

bin/pulsar-admin clusters list
us-west(local)
us-east
us-cent

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[codelipenghui]

@Technoboy- The change will introduce a new option to the existing CLI. It should start with a PIP for any public API changes.