feat: add support for the new guardrails result payload

[apetraru-uipath]

Simplify Guardrails Service Response Handling

Summary

Simplified the GuardrailsService.evaluate_guardrail() method to prioritize the new API response format while maintaining backwards compatibility with the legacy format.

Changes

Implementation

• Simplified response parsing logic: The service now checks for the new result field first, then falls back to the legacy validation_passed field for backwards compatibility
• Removed complex skip field handling: The simplified implementation no longer processes the skip field from legacy responses, as the new API format uses the result field directly

Benefits

• Cleaner code: Reduced complexity in response parsing logic
• Better maintainability: Clearer separation between new and legacy API formats
• Future-ready: Aligned with the new API response format while supporting legacy clients