Support namespaces policies updates in batch

### Search before asking

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

### Motivation

For several namespaces, it's long operation to update all their policies when we want to apply the same policy.

### Solution

Implement batch policies update for a list of namespaces.

### Alternatives

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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

No files, tests, or entry points are named. Start by locating the existing namespace policy update operation and clarify the batch API, supported policies, failure behavior, and completion criteria before estimating the change.

Written by the indexing model from the issue text.