Make RunTier0Tests.py project agnostic

As @jchapman discovered, RunTier0Tests.py in non CI mode only works in Athena, but not in AthSimulation. I made the release detection project agnostic by:

• Using AtlasVersion instead of Athena_VERSION
• Using LCG_PLATFORM instead of Athena_PLATFORM

I suppose our platform naming is always compatible with the LCG one.

@amete, this will need your approval.