[Feature flag] Rollout `feishu_integration`

Summary

This issue is to rollout the feature on production, that is currently behind the feishu_integration feature flag.

Owners

• Team: Dev1
• Most appropriate slack channel to reach out to: #dev1
• Best individual to reach out to: @chaomao
• EM: @daveliu
• PM: @lpeng1991
• QA: @TomHeng