Various small improvements in TriggerValidation

Several small improvements in Trigger ART testing are made (separate commits):

• exclude PID from log comparison in athenaHLT, as it is of course always different
• use the new python script regtest.py instead of the old perl version regtest.pl
• run log merging only for steps which produce logs
• make the ZeroCounts check have an effect on the final test status code
• improve histogram handling for tests using OH monitoring - now the relevant histograms are copied from the OH output to expert-monitoring.root which is the file expected by several post-exec steps
• make histogram merging step print a warning and exit if the input files don't exist

This merge request affects 4 packages:

• Trigger/TrigValidation/TrigP1Test
• Trigger/TrigValidation/TrigUpgradeTest
• Trigger/TrigValidation/TrigValTools
• Trigger/TrigValidation/TriggerTest

Adding @hartj ,@jpanduro as watchers

added Trigger master review-pending-level-1 labels

CI Result SUCCESS (hash 77852524)

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 9863]

added review-approved label and removed review-pending-level-1 label

mentioned in commit ca470e52

merged

added sweep:ignore label

mentioned in merge request !30622 (merged)

mentioned in merge request !30806 (merged)