[Backend] Add feature flag check to validation service

Why are we doing this work

1. Add multiple_approval_actions feature flag to security_orchestration_policies/validate_policy_service.rb
2. Update exceeds_approver_action_limit, when feature flag is off it is 1 when on it is 5
3. Add tests

Relevant links

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

Verification steps