Run RPC quickstart with java sdk; 在 RPC quickstart 中添加 java demo

[seeflood]

What would you like to be added:
Currently users can run Layotto state API & sequencer API quickstart with Java sdk, which is friendly for Java developers who don't have golang environment on their laptop. See https://mosn.io/layotto/#/en/start/state/start
and
https://mosn.io/layotto/#/zh/start/sequencer/start

Next, we need to support running RPC quickstart with java sdk.

Reference:
文档贡献指南

Why is this needed:
#67

[pepsiss]

我想试试

[seeflood]

@pepsiss Thanks! Assigned to u

Reference:
文档贡献指南

[Kelei0215]

我想试试

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[Xunzhuo]

/good-first-issue cancel
/help-wanted cancel

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity in the last 30 days. It will be closed in the next 7 days unless it is tagged (pinned, good first issue or help wanted) or other activity occurs. Thank you for your contributions.

[github-actions]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as pinned, good first issue or help wanted. Thank you for your contributions.