[RocketMQ-Connect-Runtime] Adjust runtime structure and add sample project

[odbozhou]

FEATURE REQUEST

1. Please describe the feature you are requesting.

Adjust runtime structure and add sample project

2. Provide any additional detail on your proposed use case for this feature.

Add demo project to help better understand rocketmq-connect-runtime

2. Indicate the importance of this issue to you (blocker, must-have, should-have, nice-to-have). Are you currently using any workarounds to address this issue?

3. If there are some sub-tasks using -[] for each subtask and create a corresponding issue to map to the sub task: