RegSelSvc: Move initialisation from BeginRun to BeginEvent
RegSelSvc depends e.g. on cabling provided by conditions algorithms. Move the initialisation from "BeginRun" to "BeginEvent". In addition, make all table maker tools private to avoid them being initialized by the ToolSvc.
This is only a temporary fix until the migration to a conditions algorithm is done (ATR-19657).
cc @sutt