[LigaAI] Add LigaAI integration setting page

What does this MR do and why?

Related issue: #2799 (closed)

License: Premium. Only for JiHu, SaaS and Self-Managed.

This is the 1st part of LigaAI integration MR.

• Add ligaai integration model
• Add license premium features
• Add feature flag integration_with_ligaai_issues

Screenshots

/cc @chaomao