TrigP1Test: add ART test for stop/start conditions loading

New ART test (test_trigP1_condStopStart_build.py) that simulates conditions changes during a stop/start transition as it would happen at P1 when conditions are updated during an ongoing run but only reloaded at the next stop/start.

Was hoping to be able to reproduce the crashes observed at P1 (ATR-26091) but that's not the case. Either way this is a good starting point in trying to make a more realistic reproducer.

Requires atlas-tdaq-software/HLTMPPU!33 (merged) and patch atlas-tdaq-software/tdaq-cmake!378 (merged).