Update trig-art-result-parser.sh

An updated version of this script was added to master in !20078 (merged) and swept to other branches. This MR brings the version from master to 21.3:

git checkout upstream/master -- Trigger/TrigValidation/TrigValTools/bin/trig-art-result-parser.sh

The changes include adding the second command line argument for list of steps to check and adding some comments in the script

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