athenaHLT: move post-exec into central places

When running the HLT, we used several post-execs after the user job options to ensure certain services and CondAlgs are configured correctly. Move all these settings into the source packages and use the Trigger.Online.isPartition flag to check if we are running the HLT (for legacy job options, we are using isOnline and the existence of HltEventLoopMgr). To make sure these settings are not being tinkered with, !60477 (merged) has introduced a check in the CI for the correct values of these job options.

Also, use a locked clone of the flags for TrigServicesCfg. The main flags need to remain unlocked until the user job options are parsed.

Relates to ATR-26800.