TrigValidation: Introduce threshold for warnings count in event loop
We already enforce the maximum number of INFO, DEBUG, VERBOSE and "other" messages in two tests in TriggerTest (one of them is part of CI). With this MR we start enforcing also the maximum number of WARNINGs. The threshold is set above the current number of WARNINGs. Once we manage to resolve them, we will lower the threshold.
cc @smh