TrigValidation: MessageCount updates
The following changes are made:
- Change the message count thresholds configuration interface (a single dictionary instead of individual properties)
- Add an option to print all messages of a given level if their number is above the corresponding threshold
- Skip merged log files in MessageCount to avoid executing it twice on the same messages
- Make the MessageCount step required in the TrigP1Test test which is part of CI
The main motivation for 2. (and this MR in general) is to be able to see the messages causing CI failure if the CI fails due to an excess of messages added in a MR.