[onboarding]Add learn_gitlab template

What does this MR do and why?

Relates: #1721 (closed)

• 替换learnGitlabProject的路径和模板,是自动生成的learnGitlab 的issue模板替换为中文

• 修改Notes::UpdateServices 使用户assign自己的时候能触发机器人的第一条回复
  

  新增回复

  

• 增加 FeatureFlag 把所有功能隐藏在FeatureFlag之后，这个FeatureFlag 可以以用户为维度开启

Screenshots or screen recordings

改动对比

Before: After:

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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