TrigInDetValidation: fix conditions for Run4 MC tests

Hello,

This MR is fixing the conditionsTag used in ID trigger ART tests. In !72201 (merged) , a conditions override was implemented in TrigInDetArtSteps, such that all MC tests would get the same override, namely we enforced the MC23e tag OFLCOND-MC23-SDR-RUN3-05. However this is not suitable for Run4 tests, which need a Run4 conditions tag (OFLCOND-MC15c-SDR-14-05 is currently in use). Therefore, the override was moved to TrigInDetValidation_Base, "one level lower", which gives more flexibility. If no "conditionsTag" is specified in a test, OFLCOND-MC23-SDR-RUN3-05 is enforced, otherwise, we use the specified global tag. Fixes ATR-29605.

Cheers, Bertrand