Enhance startup script for ShardingSphere-Proxy

[TeslaCN]

Feature Request

Is your feature request related to a problem?

Sometimes we try to start a new Proxy process before stopping the previous. In this situation, the new Proxy will fail to startup and we won't know it until we check the log.

Describe the feature you would like.

• Support using $JAVA_HOME.
• (Optional) Check if the address and port which we attempt to use in new Proxy process is already used by another Proxy.
• Consider how to join the script until the Proxy startup succeeded or failed.
• (Docker) Make container down if ShardingSphere-Proxy startup failed.

[sunkai-cai]

please assignees to me