athena+AthConfigFlags: unify perfmon/pmon command line options

Replace the --pmon MODE command line option with --perfmon [MODE] for legacy and CA mode. For example:

• --perfmon: runs FastMonMT in legacy and CA
• --perfmon MODE: selects the given mode (fastmonmt, fullmonmt)

The non-MT PerfMonSvc can still be selected via --perfmon perfmon if needed.

Additional changes:

• add PerfMonMTSvcCfg to MainServicesCfg
• make PerfMonConfigHelpers also work for non-transforms
• TrigValSteering: adapt to --pmon/perfmon renaming
• TileRecEx, TileMonitoring, Run3DQTestingDriver: use default --perfmon command line argument instead of re-implement it (cc @harkusha @ponyisi)

cc @wlampl @amete @cmarcon @tovsiann @tadej