[Discuss] Shall we record pulsar cluster name in bookeeper ledger metadata?

### Search before asking

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

### Motivation

Now we record the ledger component, ledger name in the bookeeper ledger metatda.

If the user use multi pulsar cluster corresponde one bookeeper cluster, we can't differ which pulsar cluster the ledger comes from in bookeper perspective.

So if we record the pulsar cluster name in ledger metadata, it can help us to do more things.

### Solution

_No response_

### Alternatives

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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

No file, test, or entry point is named, and the issue contains no proposed solution. Start by locating the BookKeeper ledger metadata handling in Pulsar and determine how the Pulsar cluster name would be obtained and represented. Done means an agreed design and tests showing ledgers from multiple Pulsar clusters can be distinguished.

Written by the indexing model from the issue text.