Wecom notification integration

What does this MR do and why?

Related issue: #3130 (closed)

License: Free. JH Only, SaaS and Self-Managed. FF

Integration Wecom just like Feishu, but without the global admin setting.

Screenshots or screen recordings

1. Wecom integtation setting page

2. Events(like push/pipeline/MR etc.) trigger to send notification to wecom groups

How to set up and validate locally

1. In rails console enable the experiment fully

   Feature.enable(:wecom_integration)

2. Visit any group or project integration page to enable Wecom integration, just like Add Feishu integration
3. Trigger the events(push/pipeline/MR/etc.) which is supported in the setting page
4. Receive the notification in the Wecom groups

/cc @chaomao