Implement API V2 system endpoints

What problem are you facing?

The current implementation of the SDK is missing the api/v2 endpoints related to system:

• GET /api/v2/system/health
• GET /api/v2/system/liveness
• GET /api/v2/system/migrations-status

How could the SonarQube SDK help solve your problem?

• Implement those RESTful endpoints
• Add unit tests for them
• Add e2e tests for them