Add observability metrics for CommandPartitionedTopicMetadata requests

### Search before asking

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

### Motivation

Currently, there's no way to track CommandPartitionedTopicMetadata requests. There's no metrics or logs that indicate that a broker is handling CommandPartitionedTopicMetadata requests.

Misconfigured clients might flood brokers with CommandPartitionedTopicMetadata requests and cause high CPU consumption.

One example of this is misconfiguration of splunk-otel-collector's Pulsar exporter. The example config configures pulsar-client-go's PartitionsAutoDiscoveryInterval setting to 1 nanosecond. I have sent a PR to fix the example config with https://github.com/signalfx/splunk-otel-collector/pull/2185 . This example shows that it's easy to mix the units and misconfigure a Pulsar client.

### Solution

Add observability metrics for CommandPartitionedTopicMetadata requests, similar to what there is for lookup requests added by #8272.

### Alternatives

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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