Support schema registry serializers for the reader

[crazyzhou]

Problem description
The schema registry offers a way to get the serialization format of the data in the stream. Flink connector can take advantage of it. Note this is a part of #362 , we plan to do it step by step.

Problem location
FlinkPravegaReader and FlinkPravegaInputFormat

Suggestions for an improvement

[crazyzhou]

With #443 , we plan to not support this feature in Flink 1.9 connector