TrigConfigSvc: delete TrigConfigSvc service
After the removal of the legacy menu support and the migration of all
clients (e.g. using xAODConfigSvc), the TrigConfigSvc only
functioned as a wrapper to create the LVL1/HLTConfigSvc. This is no
longer needed as these services are created explicitly where needed.
Also delete obsolete TrigConfigSvcConfig.py.
Further cleanup and removal of the Run-2 compatibility code in TriggerConfigGetter.py will follow in a separate MR. For the moment, maintain the current functionality.
Relates to ATR-23102.