A cleaner way to construct Session and SessionPool in Java Native API

[Jiajun Liu]

Hi all,

We have added new builder classes to construct Session and SessionPool in
Java Native API, providing a cleaner way to configure the various
parameters. Feel free to try it out and give your feedback!

*Old way:*
Session(String host, int rpcPort)
Session(String host, String rpcPort, String username, String password)
Session(String host, int rpcPort, String username, String password)

*New way:*
    session =
        new Session.Builder()
            .host(String host)
            .port(int port)
            .fetchSize(int fetchSize)
            .username(String username)
            .password(String password)
            .thriftDefaultBufferSize(int thriftDefaultBufferSize)
            .thriftMaxFrameSize(int thriftMaxFrameSize)
            .enableCacheLeader(boolean enableCacheLeader)
            .build();

Docs:
https://iotdb.apache.org/UserGuide/Master/API/Programming-Java-Native-API.html#native-apis
JIRA: https://issues.apache.org/jira/browse/IOTDB-1463

<https://issues.apache.org/jira/browse/IOTDB-1463>
Regards,
Jiajun
School of Computing, National University of Singapore