TrigUpgradeTest: delete package

Final steps in the clean-up of the TrigUpgradeTest package:

1. Move the Cosmic.py job opts and the corresponding test to TrigInDetValidation, FYI @mvozak
2. Move the newJOtest.py job opts to TriggerJobOpts as runHLT_standalone_newJO.py, FYI @tbold
3. Remove a few mentions of the package name across the repository.
4. Update two TrigT2CaloCommon unit tests to execute the athena command directly instead of relying on deleted wrapper scripts^(A)
5. Delete the TrigUpgradeTest package

Closes ATR-21713 and ATR-20514, also relevant to ATR-19150

^(A) The two TrigT2CaloCommon unit tests updated here were broken for some time, but the wrapper scripts ignored the failures and always returned code 0. This was definitely not intentional but perhaps it wasn't noticed. Because of this, I commented out the athena command in these tests because the unit test would start (correctly) failing after my changes. Instead, I added a message and a comment saying what needs to be done. The errors in those tests have nothing to do with this MR. FYI @damazio, @tbold