Default TPC loopers in o2-sim

[jackal1-66]

TPC loopers are currently injected via an O2DPG external generator by creating a cocktail. This development feeds them automatically in case the TPC detector is used and transported. A collisioncontext.root file is mandatory, otherwise the loopers will be automatically turned off. In addition the GenTPCLoopers.loopersVeto parameter has been introduced to forcefully turn off the injection. This PR is linked to https://github.com/AliceO2Group/O2DPG/pull/2191, in which the collision system is automatically fed to the sgnsim step