ISSUE-12958: [Bug] Inconsistent maxMessageSize meaning between broker config and topicPolicy config.

[sijie]

Original Issue: apache#12958

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Describe the bug
Currently, we have two maxMessageSize settings.

1. maxMessageSize in broker.conf. This is used by client. It limits the size of final message payload bytes (after compression/encryption).
2. maxMessageSize in TopicPolicy, set by org.apache.pulsar.client.admin.TopicPolicies#setMaxMessageSize. It limits the size of message header and payload. See https://github.com/apache/pulsar/blob/6b8ebbd288085dc5a93a9e92706eb5f5ad397cb8/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java#L413

To Reproduce
Steps to reproduce the behavior:

1. call admin.topicPolicies().setMaxMessageSize(5);
2. Produce message with body byte[5]{}
3. Send fail with message size exceeded error.

Expected behavior
Message should produce success.

Screenshots
NA

Desktop (please complete the following information):

• OS: macOS

Additional context
NA