ISSUE-5934: Can support read/write properties from/to Message in flink pulsar consumer/producer

[sijie]

Original Issue: apache/pulsar#824636320048
Is your feature request related to a problem? Please describe.
Currently, flink pulsar consumer/producer can not read/write properties from/to Message, we hope to support it.

Describe the solution you'd like
A) For consumer,
change method deserialize(Message message)’ access level from private to proteced in class 'PulsarConsumerSource', and we can overrided it in derived class.
B) For producer,

1. add a method like following code, and we can overrided it in derived class.
   protected Map<String, String> generateProperties(IN value) { return new HashMap<>(); }
2. invoke TypedMessageBuilder.properties() method addtional in invoke(IN value, Context context) method at class 'FlinkPulsarProducer'.