[Bug] GetLastMessageId for a multi topics consumer is meaningless

### Search before asking

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

### Version

- Pulsar standalone: 2.10.1
- Pulsar client: master (b6f0f91e)

### Minimal reproduce step

```java
final String serviceUrl = "pulsar://localhost:6650";
final String topicPrefix = "test-topic-";
@Cleanup PulsarClient client = PulsarClient.builder()
.serviceUrl(serviceUrl)
.build();
final List> producers = new ArrayList<>();
for (int i = 0; i < 2; i++) {
producers.add(client.newProducer(Schema.STRING)
.topic(topicPrefix + i)
.create());
MessageId id = producers.get(i).send("msg-" + i + "-0");
System.out.println("XYZ sent to " + id);
}
final List topics = producers.stream().map(Producer::getTopic).collect(Collectors.toList());
@Cleanup final Consumer consumer = client.newConsumer(Schema.STRING)
.topics(topics)
.subscriptionName("sub")
.subscribe();
final MessageId lastMessageId = consumer.getLastMessageId();
System.out.println("XYZ last message id: " + lastMessageId);
try {
consumer.seek(lastMessageId);
} catch (PulsarClientException e) {
System.err.println("Failed to seek: " + e.getMessage());
}
@Cleanup final Reader reader = client.newReader(Schema.STRING)
.topics(topics)
.startMessageId(lastMessageId)
.create();
reader.seek(lastMessageId);
```

### What did you expect to see?

All topics are seeked to the last message id.

### What did you see instead?

The consumer failed to seek because the mssage id can only be earliest or latest for a consumer.

```
Failed to seek: java.util.concurrent.ExecutionException: org.apache.pulsar.client.api.PulsarClientException: Illegal messageId, messageId can only be earliest/latest
```

Regarding the reader, it failed with NPE.

```
java.lang.NullPointerException: Cannot read field "ledgerId" because "other" is null

at org.apache.pulsar.client.impl.BatchMessageIdImpl.(BatchMessageIdImpl.java:53)
at org.apache.pulsar.client.impl.MultiTopicsConsumerImpl.(MultiTopicsConsumerImpl.java:142)
at org.apache.pulsar.client.impl.MultiTopicsConsumerImpl.(MultiTopicsConsumerImpl.java:115)
at org.apache.pulsar.client.impl.MultiTopicsReaderImpl.(MultiTopicsReaderImpl.java:126)
at org.apache.pulsar.client.impl.PulsarClientImpl.createMultiTopicReaderAsync(PulsarClientImpl.java:636)
```

### Anything else?

_No response_

### Are you willing to submit a PR?

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