[imporve] Improving Geo-Replication Observability

### Search before reporting

- [x] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### Motivation

Currently, we can get the replication status from Topic Stats. However, the stats include a lot of information unrelated to replication, leading to significant unnecessary overhead during queries. Additionally, we can only get this data asynchronously via Metrics. Perhaps we could split this monolithic admin API or independently query the Replicator's status？

### Solution

_No response_

### Alternatives

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Start by examining the Topic Stats admin API and the Metrics path that currently expose replication status. Compare their replication-related data with the unrelated stats and investigate how the Replicator status could be queried independently. Done means the required observability data is available without fetching the full set of Topic Stats.

Written by the indexing model from the issue text.