Support rich initialization modes of RocketMQSource

[deemogsw]

perfect new features for new Source interface and sql connector. detail in #59

[deemogsw]

bugs about RockerMQSource in current master branch:

• [x] [bug]PartitionDiscoveryIntervalMs can't set to negative
• [x] [bug]Idle source task can't be released automatic
• [x] [bug]Offset didn't commit to broker in RockerMQSource in phase of checkpoint
• [x] [bug]Records can't arrive to sink() in UNBOUNDESS mode
• [x] [features]Commit offset immediately when checkpoint is disable
• [x] [features]Support rich initialization modes
• [x] [features]Metrics with new source
• [x] [features]Boost for flink-sql-connector

[lizhimins]

I can help review pull requests.