Expose YAKS metrics to Prometheus observability

[christophd]

Collect test run metrics and expose to Prometheus observability.

Possible metrics to collect:

• yaks_reconciliation_duration_seconds: technical time to reconcile, to notice differences when load increases
• yaks_test_execution_seconds: we measure the time from when the test is created to when it is finished
• yaks_test_results_failed: failed tests
• yaks_test_results_skipped: skipped tests
• yaks_test_results_success: successful tests
• yaks_test_results_errors: error tests